The human immune system responds to viral infections in two ways. The first is the innate immune system. It is the first line of defense in our body and the only one that exists in many multi-cellular organisms. It involves certain kinds of immune cells that recognize pathogens. These cells immediately attack and ultimately destroy the infection-causing microbes. One may find the classical video showing a macrophage engulfing a bacterial cell interesting (https://www.youtube.com/watch?v=JnlULOjUhSQ). However, the innate immune system is not specific and does not form a memory against infections.

The second and more specific type of immune system is called the adaptive immune system. As the name suggests, it is specific and can build immunity against certain kinds of infection. Compared to the innate immune system, it is slower, but its high specificity makes it a powerful defense mechanism. The adaptive immune system is present only in jawed vertebrates, as it requires several macromolecular systems, which are found only in more complex organisms.

One of the main parts of these complex molecular systems forming the adaptive immunity is called the antigen processing. This refers to the presence of small particles on the cell surface. This process requires the transportation of these antigens from the inside to the outside surface of the cell. The plasma membrane of the cell is semi-permeable to chemicals and small molecules. Only small, uncharged, hydrophobic molecules can diffuse through these membranes. However, antigens are usually small pieces of proteins that are charged. Therefore, the transport of antigens through the plasma membrane is not an easy task. This difficult task is done by a special transporter, called the transporter associated with antigen processing (TAP).

In order to transport antigens across the membrane, TAP uses adenosine triphosphate (ATP) as its energy source. For almost a half century, scientists tried to understand how these molecules transport their substrates across membranes [1]. Although biochemical studies have taught us a lot, there is still more to be discovered. Years of research resulted in different models that explain how TAP works and why it needs energy. A recent finding helped to shape the working model to its current form, while also explaining that very important question: why does TAP need energy?

The working model of membrane transport assumes that TAP has two main conformations [2]. In one of the conformations, the antigen binding site is open to one side of the membrane. In the other conformation, the binding site is open to the other side of the membrane. This allows the antigen to be transported from one side of the membrane to the other. However, one major question this model raises is why TAP doesn’t allow the antigen to leak back.

This would be a deadly issue if it was the case for the cell. We know that this does not happen, but we don’t know why it doesn’t happen. Scientists have been trying to tweak their models to fit a one-way transport mechanism.

The recent study mentioned above showed that TAP works in one direction only, confirming the predictions. The study also addressed why TAP needs energy, i.e., ATP hydrolysis. Energy is needed to ensure that the antigens do not leak back. This finding also makes sense when other transporters that do not need energy are considered, simply because they can work in both directions. In short, TAP uses energy only when it “swallows” the antigens to the other side of the membrane while making sure they don’t leak back.

The proper functioning of TAP is critical for human health. Genes encoding TAP have been shown to have nearly 100 single nucleotide polymorphisms (SNPs), the variations in the human genome. Some of these SNPs cause immune deficiencies in certain individuals or populations. These SNP studies further highlight the importance of TAP.

The story told above is taking place in our cells all the time. Even when we fall ill and rest in bed, the adaptive immune system and TAP fulfill their roles and help our body recover.

References

1. Jardetzky, O., Simple allosteric model for membrane pumps. Nature, 1966. 211(5052): p. 969-70.
2. Grossmann, N., et al., Mechanistic determinants of the directionality and energetics of active export by a heterodimeric ABC transporter. Nat Commun, 2014. 5: p. 5419.

The word “obesity” originates from the Latin obesus, which literally means, “having eaten until fat.” Obesity is a disorder involving excessive body fat that damages our well-being and increases the risk of health problems. For example, an obese individual is ten times more likely to have heart disease and five times more likely to have diabetes as opposed to a person of normal weight. Some other symptoms of obesity are high blood lipids (e.g. triglycerides), high blood pressure, and low good cholesterol, which helps remove bad cholesterol from your arteries. Besides leading to a number of diseases, the large waistline formed due to the fat buildup also triggers our immune system, which plays a critical role in the initiation and progression of obesity-associated diseases. Before going into the details of the altered immune response due the increased storage of fat, let’s first explore the perfect order in our immune system, especially in a subset of immune cells called macrophages.

The amazing immune system

Our astounding immune system is in charge of defending our body by clearing out thousands of germs that can make us sick. Our immune cells serve in the context of cleansing the human body from invading germs. The immune system has two branches: the innate and adaptive branches, as defined with respect to the characteristics of their responses. The cross-talk and mutual communication between the two arms constitutes the integral immune response.
The adaptive immune system operates slowly, by developing for specific pathogens. In addition, it has a memory of previous exposures. The innate immune system provides a first line of defense against the invasion of disease-causing microorganisms (pathogens). It has three defense layers: anatomical barriers, humoral barriers, and cellular barriers. The skin is an example of the physical barriers, which prevent pathogens from getting access to our body. The chemicals found in tears, saliva, and mucus impair bacterial growth, and they represent the humoral barriers. Once an invading bacterium somehow evades these barriers, or a tissue injury occurs, various types of immune cells are recruited to the site of infection for the protection of the host. These cells constitute the third barrier of the innate immune system. As an initial defense system, innate immune cells and their components exhibit a fast, non-specific response with minimal memory of past exposures.

Macrophages: the big eaters

Macrophages, a subgroup of such innate immune cells, form a front-line component of our bodies’ defense. The term “macrophage” is derived from a combination of two Greek words – “macro,” meaning big, and “phage,” meaning eater. As the early combatants of our immune system, they are armored with perfectly-tuned ingestion capabilities. Macrophages function like the policemen of our body because they are charged with patrolling nearly all of our body’s tissues, except the heart. They are intensely positioned in tissues where infections are likely to arise, such as the gut and lungs.

There are approximately 200 cell types in our splendid body. Each specialized type of cell is charged to operate like a government or an army. Macrophages are organized to be combative and to secure the body. They possess flawless intelligence, coordination, communication, and movement traits. They are created from differentiating monocytes. Monocytes are produced in the bone marrow and then released into blood circulation. In case of an infection or dangerous threat, they migrate into tissues as early combatants.
To collect intelligence, macrophages are equipped with a large repertoire of sensors or receptors, which are positioned in the cellular membrane and intracellular part of the cellular architecture. These receptors are called pattern recognition receptors (PRRs), whose function is to detect certain structural patterns of pathogens such as bacteria, viruses, parasites, and fungi. Such specific patterns are named pathogen-associated molecular patterns (PAMPs). On the other hand, molecules generated by host cells under extraordinary stress are called danger-associated molecular patterns (DAMPs) which are detected by other specific PRRs. Additionally, macrophages are ornamented with other types of receptors that help recognize and eat extracellular material, including pathogenic microorganisms by a membrane-bound vesicle. This process is phagocytosis, where the pathogen-containing vesicle is ultimately fused with the degradation machinery of the cell (i.e. lysosomes) to eliminate the pathogen.

Once the intelligence is collected by sensors, macrophages become “activated,” meaning that they are mobilized by transmitting and processing the information into the interior of the cell via – from a biologist’s perspective – downstream signaling pathways that initiate the program in the cell nucleus to secrete “alarm” molecules. Such molecules are named cytokines, whose duty is to adjust immune response by aiding cell-to-cell communication and stimulating the movement of macrophages towards the combat zone – in other words, the sites of inflammation.

Metaflammation: a chronic disease caused by obesity

The areas possessing redness, heat, pain, and swelling represent the combat zones of classical inflammation. Such wars are usually short-term and area-specific, with respect to infection and injury; they end with the elimination of the infection and the repair of the damaged tissue, respectively. Unfortunately, chronic inflammation is a different type of prolonged and disorganized immune response. Such a chronic state manifests, a) a low grade increase in immune system markers (inflammation-inducing cytokines); b) a persistent stress response; c) inflammatory effects covering the whole body rather than localized symptoms; and d) a sustained state of the disease. In other words, chronic inflammation corresponds to a lasting state of low-level war all over our body that gradually escalates and leads to various chronic diseases. Interestingly, intense research on the obesity epidemic demonstrated the presence of such low-grade chronic inflammation as the main driver of obesity-associated diseases such as insulin resistance, diabetes, atherosclerosis, pulmonary hypertension, and chronic liver disease. Such an inflammatory state is also termed metabolic inflammation or metaflammation.

The molecular details underlying metaflammation are increasingly better understood. From a scientific standpoint, obesity is characterized by the increased storage of lipid molecules in an expanded fat tissue mass. The macrophages residing in such fat tissues of obese individuals are likely the major source of inflammation-inducing (pro-inflammatory) cytokines, as they seem mobilized mainly due to two reasons. First, the excessive presence of lipid molecules accumulated by overeating are sensed as danger-associated molecular patterns (DAMPs) by various macrophage sensors. Second, macrophages residing in fat tissues have significantly higher level of threat sensors, leading to their easy mobilization. Therefore, the level of such sensors in obese individuals was found to be directly correlated with the severity of obesity-related diseases, such as diabetes and insulin resistance. Moreover, fat tissue macrophage populations are directly associated with the accumulation of fatty tissues in different experimental mouse models. The studies performed in obese and diabetic mice models and patients demonstrated high levels of pro-inflammatory cytokines in blood circulation and fat tissues, contributing to metaflammation.
To simplify metaflammation, excessive fat buildup is sensed as a threat by the big-eating patrollers of our amazing immune system, leading to their abrupt mobilization and continuous secretion of cytokines as “alarm” molecules. The intensity and locality of cytokines simply determines the state of war (i.e. the category of inflammation). In obese individuals, the low concentration of cytokines in blood circulation and fat tissues represents an ongoing low-level war found all over the body, which is metaflammation. Paradoxically, the degree of the war escalates by the enhanced sensitivity of macrophages to cytokines and the gradual increase of cytokines as a result of additional fat accumulation, hence throwing the body out of order and making it vulnerable to numerous diseases.

Apart from excessive food intake, there are other nutritional, environmental, and behavioral factors that give rise to similar chronic inflammation in our bodies. Things such as processed food, traffic-related air pollution, inactivity, inadequate sleep, and stress, can have similar effects as obesity. To protect our splendid bodies from the harmful effects of chronic inflammation resulting from overeating and other factors, we need to carefully think about our external and internal responsibilities. We may need to make intensive, external lifestyle changes, including restricted energy intake, more exercise/physical activity, and a diet high in healthy, unprocessed foods.
As for the internal responsibilities, the most essential part is strengthening our self-control. By doing so, we may improve our willpower, which is needed to resist the temptation to overeat. Otherwise, disrupting the balance of our wonderful body by overeating is an offense and disrespect to its perfect order. Such an imbalanced state pushes our body further toward a biological cliff, to such an extent that the delicately and perfectly organized immune system declares war against the harmful lipid molecules and leads to the emergence of various inflammation-associated diseases. Therefore, to eliminate the risk of imbalances in our superbly designed bodies, we have many internal and external responsibilities to fulfill.

One of the processes that occurs in the body is called “inflammation.” Inflammation occurs when a cut into the skin also punctures a blood vessel. This situation directly exposes the blood to the air. Inflammation occurs in a few steps. First, the blood vessels near the wound are expanded (which causes the swelling that we see near the cut) and special proteins called “fibrins” are brought in. These fibrins bind to each other to form a net-like structure. We are all quite familiar with this net, which we call a blood clot. This net stops the bleeding and cuts the interaction between the air and the blood within a few minutes.

Next, it is time to quickly eliminate any foreign objects that got into the tissue. Special immune cells called “macrophages” are sent to the crime scene to clean up. Macrophages are large white blood cells that “eat” microbes and other foreign objects using a process called “phagocytosis.” After the scene is all cleaned up, these macrophages excrete special molecules that induce tissue repair and return the blood flow to normal. An important note here is the specific order of these events. Like every single process in the body, they occur in the most purposeful way possible. What do I mean? I mean that, first the wound is closed urgently; second, macrophages are sent in; third comes the tissue repair. Any other order would have greatly lowered the effectiveness of inflammation. Imagine that the wound is closed after the macrophages are sent in. Then, by the time the macrophages killed all the microbes, twice as many would have entered the scene. The body seems to know every single event beforehand and plans its defense accordingly.

Our body is perfectly calibrated to keep our blood, the milk of our organ systems, absolutely pristine.

Let’s say a microbe managed to sneak into the blood before inflammation occurred, and is long gone to another region of the body. Does the microbe win? Unfortunately for the microbe, it has to pass another test. This time the tester is the lymphatic system. The lymphatic system is the sewage system of the body. When the blood transfers its nutrients to the tissue, the fluid goes through the “interstitial area” (the empty space between organs). During this process, some of the fluid stays in this area and starts to accumulate. This is where the lymphatic system kicks in. The lymphatic system consists of many tubes running parallel to the blood vessels and recollects any excess fluid and transports them to the subclavian vein near the neck. This way, excess fluids of the body and all of the molecules in them, are reintroduced into the circulation. If there is a problem with this process, an abnormality called “edema” occurs. Of course, the blood is a very sensitive fluid because it travels through the whole body and seeps into almost every single cell. If a microbe were to get into it, it would easily spread and cause disease. So, the lympatics first does a checkup on the body fluid. This checkup occurs at special nodes in the system called lymph nodes found all over the body. Two of the most famous lymph nodes are the spleen and the tonsils. Within these nodes are lymphocytes, special immune cells that “tag” bacteria and other microbes to be later destroyed by macrophages. Thus, the blood is continuously cleaned and kept safe from harmful microbes.

Last but certainly not the least, the final inspection the blood goes through takes place in the kidneys. The aforementioned two checkpoints prevent the entrance of any foreign materials into the blood, and the elimination of any microbes lucky enough to somehow make it through. So, the only task to be completed is the elimination of excess molecules formed in the metabolism. For example, the blood in the veins (the vessels that carry carbon dioxide formed by the respiration of cells) is carried to the lungs where the carbon dioxide is exhaled. But, a much more precise mechanism comes into play in the kidneys. Blood vessels that come from all around the body form a knot-like structure in the kidney called the “glomerulus.” This knot-like shape increases the surface area of filtration. The blood running from the glomerulus is then filtered into the “Bowman capsule,” which surrounds the glomerulus.

But wait! The sanitation system is not satisfied with this first filtration and “thinks” that the filtrate is not ready to be excreted by the urine. So, a more delicate filtration occurs right after the filtrate enters the “proximal tubule.” While passing through this tubule, essential molecules are immediately reabsorbed into the body. The most valuable of all these molecules is glucose, since it is the main source of energy in the body. The proximal tubule reabsorbs around 98 % of all the glucose, while the distal tubule scouts out the rest. After the tubules are done with the filtration, not a single glucose molecule is left in the urine. As a matter of fact, the presence of even a few glucose molecules in the urine leads to a diagnosis of “renal glycosuria.”

After the proximal tubule, the filtrate goes into the “loop of Henle,” where it is dipped into a high-concentration environment. Water travels passively (without the need for energy) from low-concentration to high-concentration areas. In the loop of Henle, the urine is low-concentration, so water runs back into the body. Thus, any excess water in the urine is effectively and economically reabsorbed. The big machine that consists of the glomerulus, the Bowman capsule, the tubules, and the loop of Henle is called a “nephron.” Everything described above occurs in a single nephron. The average number of nephrons in one kidney is around 1,000,000. The human bladder holds around 150 ml of urine on average. So, each nephron is actually responsible for 0.00015 ml of urine production. The kidneys filter over 1,000 liters of blood each day, so our blood is kept just as we want it. Millions of tiny nephrons work in unison to take in huge amounts of blood and they know exactly what to leave and what to keep, 24 hours a day, 7 days a week.

Our blood is our life source. It is the milk of the organs, and our organs would dry up without it. Believe it or not, our organs are quite picky. If they are to receive anything they don’t like, they will start acting up. In order to keep the organs happy, the three mechanisms mentioned above have to work hard and not make a single mistake. These mechanisms are, of course, also made up of cells. These miniscule cells “know” exactly what their clients on the ends of the body like and don’t like, and prepare the blood composition accordingly. Only one word can describe these wondrous mechanisms: Impeccable.

Brian Turk is a medical student from New Jersey. He writes on medicine, health, and biology on a freelance basis.

Immunity can be divided into innate immunity and acquired immunity. The mechanisms of innate immunity are given to us by our Creator as a tool with which to protect ourselves. These are used to fight against every kind of microorganism. These ever-ready forces do not need to have met the enemy microorganisms to fight them off. Acquired immunity comes about after the infectious microbe has been encountered; this is usually as a result of infection or vaccination. Such immunities only protect the body against a specific harmful organism. T and B lymphocytes and antibodies belong in the acquired immune system, whereas other mechanisms are part of the innate immune system. We can classify the very intricate immunity mechanisms as follows:

A – Layers that cover the inner and outer surfaces of the body: These are the physical structures that carry out the task of protection by covering the tissues like a shield or fortress.

1. Skin: Our skin is an organ in its own right. It is created with such perfect characteristics that no microorganism can penetrate our body if there are no flaws, like gashes, scratches, or wounds.

2. Oral mucous membrane: If the epithelial layer covering the interior walls of our mouth is healthy, microorganisms cannot infiltrate the blood.

3. Areas around the sexual organs: The sexual organ in males is, even at birth, more protected than that of females. For female children, the epithelium covering the interior face of the organ turns into a multi-layered structure due to the impact of estrogen (sexuality hormone) that starts being secreted after adolescence. That multilayered structure blocks infections that can result from sexual intercourse. Female children before adolescence do not have estrogen, thus their genital organs have a thinner layer of epithelium and are more likely to be infected. This is why cleansing after urination should be done from the front to the back and the genital organs should not come into contact with feces. Our God of infinite mercy also gives girls a hymen in order to protect girls from germs.

B – Flora bacteria (beneficial bacteria): These do not serve as mechanical obstacles, but are assigned tasks. There are some bacteria that do not cause illnesses in the urine and in the proliferation canals, the skin, throat, intestines, and the eyes. Those beneficial bacteria located in our body work for us and hinder other infectious bacteria from settling in these zones. Those places are sterile in the body of a fetus; no beneficial bacteria exist there. Protector bacteria are positioned in those places right after the birth; this is a revelation of God’s infinite compassion. For instance, a baby’s first feces are sterile because there are no bacteria in his intestines. As time passes, a baby adopts protector bacteria through his mouth by nursing, from bottles, and pacifiers. Parents should be careful about the purity of pacifiers, feeding bottles, water, and additional nourishments, particularly in the first couple of months, until the bacteria flora have been established in an infant’s body. Otherwise, babies can easily suffer from diarrhea. God equipped beneficial bacteria with some special peculiarities to be able to deter other microorganisms from settling in the body. Here are some of these peculiarities:

1. They compete with infectious bacteria on the consumption of nutrients, so they restrain the reproduction of other bacteria.

2. They emit bactericides that kill only pathogenic (harmful and infectious) bacteria.

3. Some flora bacteria are assigned a mission to impede the reproduction of pathogenic bacteria so as to reduce pH (increase acidity) in the environment. For example, the lactobacillus in the female genital passage produces lactose by breaking down the glucose in the uterine canal in order to acidify the secreted matters in that canal. Reproduction of fungi is also obstructed in the same way. Due to that fact, some fungal diseases might emerge in genital areas or in the ears, among other places, after antibiotic treatment. Antibiotics kill not only pathogenic bacteria, but also flora bacteria. Thus, desultory usage of antibiotics should be avoided.

Today, beneficial intestinal bacteria are taken orally in capsules, and infectious bacteria in the intestines are killed by supplementing the flora bacteria in that organ without the use of antibiotics.

C – Mechanical cleansing:

1. Secretions:

a.Saliva: Secreted continuously from the glands behind the ears, beneath the chin and beneath the tongue, saliva expels the intruder pathogenic bacteria by cleansing our mouths. It also prevents tooth decay and gum inflammation by cleaning leftover food on which bacteria could feed.

b. Tears: Tears are charged with the duty of cleaning the conjunctiva (the mucous membrane that lines the inner surface of the eyelids and that continues over the forepart of the eyeball) and the cornea (the transparent part of the coat of the eyeball that covers the iris and pupil and admits light to the interior).

2.Cilia: These are feather-like cell extensions of microscopic size.

a.Nasal Cilia: Covering the nasal mucous membrane, mucus (a slimy substance) grasps dust particles and microbes in the air due to its adhesive nature. Lumpy folds inside the nose do not let the air flow straight. Therefore, a turbulent air current occurs in the nose. This turbulent current causes the particles in the air to come into contact with this slimy substance and to get stuck there. Epithelial cells also have cilia expanding toward the nasal cavity. Every cell has nearly 200 cilia. These cilia push mucus and the dust particles attached to it toward the pharynx with an up and down whipping action (10–20 strokes per second) so as to keep them away from the lungs.

b.Cilia in the lower respiratory passages: The upper surface of epithelium that is spread on the trachea, bronchi, and bronchioles is also covered with mucus. Epithelial cells in this area have cilia, too. These cilia do the same whipping action to push particles and microorganisms in the mucus toward the pharynx. They are pushed into the pharynx and expelled by coughing. One of the damaging impacts of nicotine on the respiratory system is that it paralyzes these cilia and disrupts the discharging process of harmful particles. As a consequence, smoking leads to many lung diseases.

D – Enzymes, acids and antibodies in body secretions:

1.Lysozyme: This is a substance found in body secretions (saliva, perspiration, tear, genital organ secretion etc.) that kills bacteria.

2.Stomach acid (Hydrochloric acid, HCl): Being emitted through stomach glands, HCl is a strong acid that can destroy bacteria that are able to reach as far as the stomach with the food we eat. Although we usually have our meals without cleaning our hands sufficiently or without washing them thoroughly, we rarely (except for situations where we are exposed to a high density of microbes like food poisoning or dirty drinking water) get infected via this route. The actors in this perfect protection are lysozyme and stomach acid.

3.Antibodies: Being present in the blood and body secretions, antibodies play a role in the defense against microorganisms. Antibodies in breast milk are passed from the mother’s blood to her milk via a very special mechanism, and are significant in the protection of an infant from infections.

E – Defender Cells: Resembling special operation forces, each of these cells is trained in different parts of the body and sent into the blood circulation. Those troop-like cells, which protect us against diseases by struggling fiercely with germs that can reach the blood after overcoming many obstacles, cannot have come about merely by chance, without the participation of the All-Knowing Designer.

1.Macrophages: Monocytes, a kind of leukocyte in the blood, pass from the capillaries to the tissue and turn into giant cells called macrophages that can phagocytose (swallow microbes) at a great rate. Macrophages swallow and tear down every kind of bacteria and virus that invades the body. These cells constitute the first defense line of the body and serve like advance guards. For instance, the first force to start fighting against the germs that can penetrate the skin through a scratch is the macrophages found just beneath the skin are called histiocytes. Germs that can infiltrate the blood through the intestines and reach the liver via the portal vein are eradicated by another type of macrophage. Therefore, almost no bacterium can pass from the intestines into the general blood circulation system. Germs that enter the body orally are destroyed by macrophages stationed in the lymph nodes on the tonsils. The ones that manage to reach the lungs through the respiratory paths are killed by the macrophages in the alveoli. Those cells also cause T-lymphocytes (very specially equipped cells) to proliferate by stimulating them. 2.Neutrophils: These are the most common type (60-70%) of leukocytes. These cells participate only in fights against bacteria. When bacteria enter a tissue, some poisonous matters emitted by them cause a chemical reaction called chemotaxis; this reaction attracts the neutrophils toward the infected tissue. In this case, the neutrophils leave their capillaries for the infected tissue and find and destroy the bacteria. How can germ-eating cells, like macrophages and neutrophils, distinguish normal body cells from microbes? Undoubtedly, the Creator of such an excellent defense system does not make us worry about such a problem; it was for this purpose that God created opsonins. Opsonins are similar to adapters in that they are able to attach two different parts together and connect themselves to a specific place on the germ. Thus, macrophages and neutrophils carry out their germ-eating job perfectly, connecting themselves to those opsonins. Since our own body cells do not have receptors that can handle opsonins, they cannot be eaten. 3.Lymphocytes: These are the troops of the immunity system with the most complicated organizations and strategies. These troops are categorized as T and B lymphocytes. They are the most important and powerful of the immunity mechanisms and constitute about 20-30% of the leukocytes in blood. They are regarded as the last defense line against those germs with which the other mechanisms cannot cope. a.T lymphocytes: When T lymphocytes are stimulated by macrophages, T cells that are a form of T lymphocyte secrete a matter called lymphokine. Lymphokine stimulates cytotoxic (microbe killer) T cells and B lymphocytes into action. Unless auxiliary T cells exist, the acquired immunity system collapses. Likewise, the HIV virus destroys auxiliary T cells and renders a person susceptible to disease. Even very simple infections can turn into a catastrophe for those patients. Cytotoxic T cells assault bacteria and particularly virus-infected body cells. They deliver porphyrins (proteins to make holes) into cell membranes by attaching themselves to the cells. In that way, a huge amount of water enters the cells and they get torn, due to over-swelling. Thus, viruses in the infected cells are dispersed and are neutralized by specific antibodies produced for that purpose with their infecting ability being impeded. (Viruses have to enter body cells to be able to proliferate. Only in this way can they protect themselves against antibodies and proliferate. Viruses that proliferate in cells use matters in those cells and cause them to eventually break apart, then move onto other cells.) b.B lymphocytes: These cells are stimulated directly by microbes. However, they need lymphokines to be completely stimulated and activated. Lymphokines are created capable of causing B lymphocytes to proliferate and transform themselves to Plasmocytes. Plasmocytes also emit antibodies to the blood. c.Killer cells: These play a role in the innate immune system, so they do not need stimulation like T and B lymphocytes. In particular, they assault body cells that are virus-infected or show a tendency to cancer. In this way, they establish a first defense line against viruses and block cancer development. Even though the working principles of lymphocytes are not known, they are related in some way to spiritual values such as love, enthusiasm, and peace of mind. Likewise, it is known that the immune systems of people whose spirituality has been weakened by depression and stress are more susceptible to break down. Unless those people recover by activating their spiritual dynamics, like faith in destiny, they are under a greater threat of cancer. Yet, this world is a place of examination. We cannot claim that every cancer is due to a damaged spirituality; we should not forget that cancer might occur due to different reasons. 4. Eosinophils: These are a kind of leukocytes that can kill some sort of parasites. They cling to parasites and release the granules in their cytoplasm into the parasites. These granules contain enzymes which destroy parasites. 5. Mast cells and basophils: Mast cells and basophils play a central role in inflammatory and immediate allergic reactions. They are able to release potent inflammatory mediators. Mast cells function out of the veins and protect the tissues in the body, whereas basophils are similar cells found in the bloodstream. F – Factors in plasma: 1.Antibodies: These are secreted into the blood by plasma cells. They fight against the germs that have stimulated them. They show their impact directly (neutralizing bacterial poisons, gathering and precipitating bacteria, neutralizing viruses, pulling microorganisms into pieces) or by activating a very special system called a complement. 2.Complement proteins: When inactive complement proteins in plasma are stimulated by antigens and an opposing antibody complex, active complement compounds are brought to life. These compounds have various effects like chemotaxis, opsonization, development of inflammation as a result of stimulation of mast cells and basophils, and the destruction of microorganisms. The complement system can be stimulated by microorganisms without a need for antibody development (without a need for lymphocytes); this can be seen as a manifestation of our Creator”s name Mudabbir (managing, administering, controlling every being in balance and order). This ensures the stimulation of a complement system under conditions that lack antibody production. Hence, the body is never left completely undefended. Is it really possible that such an amazing defense system, that requires unlimited knowledge and power, and that consists of every kind of alternative action, can come into existence by itself? 3.Interferons: Viruses invade body cells and synthesize proteins that contribute to their proliferation. Interferons, secreted by lymphocytes or other leukocytes, are created so that they can attach themselves to virus-infected body cells and obstruct the production of those proteins. Hence, these viruses cannot proliferate. 4.Lysozyme: Mentioned in the earlier part concerning body secretions, lysozyme is also available in the blood and kills bacteria there. 5.Properdin: This is a kind of protein available in the plasma which can neutralize viruses and destroy some bacteria types. 6.Acute phase proteins: These are a large number of serum proteins (C-reactive protein, etc.) that are swiftly synthesized by the liver and that are employed in defense during infections. 7.Beta-lysin: A substance that destroys some types of bacteria. G – Events caused by infections: 1. Inflammation: Inflammation is a response that is designed to protect tissues against tissue destruction, caused by factors like infection, excessive heat, and trauma. When a tissue is invaded by microorganisms, it starts to be destroyed; certain matters come out of those tissue cells (as mast cells) and lead to certain reactions in that zone. a.Vasodilation: As the little veins transporting blood to a tissue widen, more blood rushes in and more neutrophils are carried to that zone. Meanwhile, a color enhancement (blushing) occurs in that place. b.Increase in permeability of the capillaries: Neutrophils can penetrate into the tissues more easily. Plenty of water also passes through tissues, so some edemas (swelling in tissues) develop. Finally, coagulation proteins in the plasma, which can rarely infiltrate from capillaries to the tissues because of their large molecular structures, pass to the tissues and clot the liquid here. Hence, lymph veins, which are responsible for returning the liquid to the blood circulation, are plugged by clots. Consequently, inflammation detains microorganisms in that specific zone and prevents them from spreading throughout the body. Microorganisms are also destroyed by tissue macrophages in the inflammation zone and the migrant neutrophils working there. (The more a bacterium causes tissue damage, the harder it passes to blood.) Then, remnants of dead bacteria, damaged tissue cells, and neutrophils that are also destroyed after the phagocytosing of between 5 and 20 bacteria soften the inflammation by dissolving and creating some pus in that zone. The pus streams out by itself or is relieved by an incision being cut in the covering skin. 2. Fever:Toxins coming out of some bacteria and some secretions of microbe-phagocytosing cells lead to an increase in body temperature. Fever stops reproduction of microorganisms and kills them by ruining their structures. Within this framework, the occurrence of fever is beneficial; it indicates that the body is resisting and struggling to kill the microbes. Therefore, fever should not be reduced as long as it is not too high to cause brain damage (especially for children). 3. Cough: A cough helps the body discharge the microbes in the respiratory paths. Thus, cough medicines should not be used immediately, except in cases of whooping cough. 4. Diarrhea: This helps the body rid itself of feces quickly, so medicines to stop diarrhea should not be used, either. However, in cases of cough and diarrhea, a person should know their own strength and the strength of their immune system well and take medication accordingly. When we consider all these defense mechanisms, this question occurs in our minds: Do we protect ourselves against infections or is there someone who operates various immunity mechanisms in our bodies and controls them at every moment with His infinite knowledge and power?