blood and the immune system

The human body's immune system refers to its natural ability to defend itself and the various ways it does so. The innate system and the adaptive system, both of which will be further detailed in the paragraphs that follow, make up the majority of its two subsystems. The immune system is an essential component of the human body because it defends the body against diseases and other harmful elements. Because they are unable to defend themselves against the numerous infections that continually afflict them, those with compromised immune responses are always ill.

Innate Immune System


To go into further detail, the innate immune system is defined as the inherent capability of one's own body to protect itself from disease. This system relies heavily on the body's ability to recognize not only particles that are different from itself but also the ones that are "self" so as not to mistakenly destroy them and ultimately recruit the necessary cells to ward off pathogens that enter the body. Cells that consist this system include the lymphocytes, the monocytes, neutrophils, basophils, mast cells, etc.

Adaptive Immune System


On the other hand, the adaptive system's main mechanism is responding to any possible harmful stimuli by eliciting reactions that will localize and eliminate possible pathogens. It does this via the T and B lymphocytes and antigen presenting cells. The antibodies produced as a response to antigens present (antigen being anything that enters the body that stimulates antibody production) are a major component of the adaptive immune system.There are components of both systems that not only complement but also mirror each other. For example, chemokines and cytokines play a major role in both subsystems because they recruit the necessary cells and molecules to the area and serve to activate them. Cytokines and chemokines are a myriad of proteins with many different functions across the different systems of the human body. The main difference between them is that the cytokines are secreted by cells to stimulate receptors on other cells in order for them to find the pathogen while chemokines are a specific type of cytokine and very important component of the immune system that stimulates white blood cells to go to the areas they need to be. Both the innate and adaptive system contain similar components that ultimately lead to elimination of the pathogen threatening the normal homeostasis of the body.

Phagocytosis


Of the many processes that cytokines induce, one of the major, if not the most important, immune responses of innate immune system is phagocytosis. The term phagocytosis literally translates loosely to "cell eating" and refers to the ability of certain immune cells in the body to absorb a pathogen and digest it thereby eliminating it from harmful effects on the body. This is done by only 2 cells of the innate immune system, the neutrophils and the tissue macrophages, the predominant phagocytic cell determined by the time since injury and the area of injury. Overall, the process of phagocytosis is highly regulated by three main mechanisms: 1) the texture of the tissue surfaces is usually smooth which makes it more difficult for the neutrophils/macrophages to adhere to its wall and begin the process of phagocytosis. 2) A functional immune system secretes a certain protective protein around itself to prevent its immune system from making the mistake of destroying its own healthy cells. This is also the main mechanism in a patients with autoimmune disorders, autoimmune which literally means "immune to self" wherein the body has difficulty identifying what is "self" and "non-self" and begins its own normal, healthy cells resulting into many diseases. Thirdly, the body secretes antibodies in response to pathogens that enter the body in order to "tag" them specifically for the cells involved in phagocytosis. Collectively, these all function to preserve the human body and eliminate any threat against it. When a pathogen enters the body, like a parasite per se, the human body has already set up defense mechanisms against it. First, the skin. The human skin, also known as the largest organ in the body, also serves as the first barrier to most pathogens. The physical barrier is crucial to the body's defense mechanisms because it already arrests majority of the major pathogens to enter the human body.

Inflammation


Inflammation is also another integral component of the immune system. It refers to the immune response of walling off pathogens or harmful substances and almost always serves as the initial response, in fact, it occurs even before phagocytosis. Inflammation serves to contain the pathogen or harmful substance in order to prevent it from spreading all over the body as well as to concentrate it to an area where cells have a better access to it allowing a more efficient elimination process. However, inflammation occurs with or without a pathogen. Its many stimuli can include an IgE-induced allergic reaction, chemicals, etc. It serves as the primary response to almost any type of tissue injury. There are 5 major steps in the inflammatory process:

1. Blood Vessel Vasodilation


This occurs in the local blood vessels, usually adjacent to the area of tissue injury. The increased blood flow and tissue perfusion of oxygen allows the cells and substances to concentrate themselves upon the site of inflammation.

2. Increased Capillary permeability


For the same reason as the blood vessel vasodilation, in order for large quantities of fluid, especially ISF which contains important cytokines, chemokines, and immune cells to access the site better.

3. Clotting of the fluid


The increased amounts of fibrinogen and other proteins make it difficult for other cells and proteins not involved to disrupt the inflammatory process.

4. Migration of neutrophils and macrophages


As previously described in the section of phagocytosis, these cells enter at different times and exert their effects on the pathogen, further contributing to the phagocytosis process.

5. Tissue Swelling


Swelling, one of the most prominent and visible effects of inflammation, is often the result of tissue products that have accumulated in the walled off portion of the area of injury. This swelling is crucial to inflammation because it is also when intercellular attachments form within the blood vessels in order to allow better diapedesis.Some of tissue products that are resident in the body and are the main mediators for inflammation such as histamine, bradykinin, serotonin, prostaglandins, and more.

Adaptive Immune Response


The adaptive immune response confers a different type of immunity in that it requires a stimuli and a response to the stimuli mainly by stimulating the T cells and B cells. The B cells confer adaptive immunity by several ways including creating antibodies and tagging the for future elimination by the appropriate cells, it also confers memory so that the next a similar strain or even the pathogen itself can be recognized and eliminated much more quickly. This is the principle behind which vaccination works. It either confers you with pre-formed antibodies that will already do the job for you.. Unfortunately, this method is not only short-term because these antibodies are not as specific as if antibodies were produced by the innate immune system stimulated.

Blood and Immune System


Blood is a vital component of the living being and contrary to popular belief, it is not merely the "fluid" that brings oxygen to the body and courses through our veins but it is actually considered tissue due to the fact that by definition, it qualifies as such: it is a collection of similar specialized cells that serve particular functions and the cells are suspended in a matrix. When blood is placed into a capillary and centrifuged, its main components settle according to its specific gravities from the lightest to heavies top to bottom and one can clearly see them: the red blood cells settle at the bottom of the capillary and appear as a red heterogeneous mixture of clotted and not clotted red blood cells (depending on the presence or absence of anticoagulant in the tube), the white-gray-ish buffy coat which contains the white blood cells and platelets and at the top, the clear fluid is the serum, the very matrix that qualifies blood as a tissue. These components can be individually affected to cause some major diseases. Abnormal amounts of red blood cells, either too much or too little, would require major intervention. Slight decreases and increases greatly influence the oxygen carrying capacity of the red blood cell which could leave disastrous effects on the body. This condition would be anemia if deficient and erythrocytosis if too much. However, if the same thing should happen to the white blood cells, it could in fact cause more harmful effects that would require more than just therapeutic phlebotomy (removal of excess blood to transfusion of more of it. The process of leukemia and leukocytosis are such anxiety-inducing threats because they are often associated with cancer. The main role of the leukocytes are to defend itself against pathogens and response to the antibodies presented to them by the antibody presenting cells. Lastly, although the smallest of all the major blood components, they play a very big role in the immune system. They keep the blood fluid and you from falling to the ground but also coagulate any open wounds or torn tissue in order to create the primary hemostatic plug, a temporary closure of wounds in the body to preserve tissue integrity and maximize the healing process. Diseases that presented with structural or specific defects in the red blood cell are called hemoglobinopathies and often interfere with sleeping habits and eating.

Works Cited


Fauci, Anthony S. Harrison’s principles of internal medicine. Vol. 2. New York: McGraw-Hill, Medical Publishing Division, 2008


Goodara, Hemant. The Washington manual of medical therapeutics. Lippincot Wiliams, 2013.


Hall, John E. Guyton and Hall Textbook of Medical Physiology E-Book. Elsevier Health Sciences, 2015.


Kumar, V., Abbas, A. K., Fausto, N., & Aster, J. C. (2014). Robbins and Cotran Pathologic Basis of Disease, Professional Edition E-Book. Elsevier Health Sciences


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Murray, Robert K. “Harper’s illustrated biochemistry.” (2009): 472.

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