Immune System: Definition, Function, Disease, and Types


The immune system is the body’s defense against infection. The immune system (ih-MYOON) attacks bacteria and helps us stay healthy.


Collection of internal structures and processes — to prevent diseases or other foreign objects that may be damaged. During normal operation, the immune system recognizes various threats, including viruses, bacteria, and parasites, and distinguishes them from the body’s own healthy tissues.

 immune system

Immune System Structure Biological

Immunotoxicology is the study of damage to the immune system, which may be due to occupational, careless or therapeutic exposure to various environmental chemical substances or biological substances. There are two broad research areas in this area: one that includes immunosuppression. Another study involved increasing or overestimating an immune response, such as allergy or autoimmunity. The immune system is a passive target of inhibitory heterologous organisms.


Due to the host’s inability to cope with it, exposure to inhibitory heterologous organisms will lead to the rise of infectious diseases or neoplasia. When the immune system reacts to other foreign organisms, the specific immune response will increase substantially and health will be adversely affected, such as respiratory allergies (such as asthma and rhinitis), allergic contact dermatitis, or autoimmune diseases. Therefore, although other tissues may be affected after changes in immune response, the immune system is the main site of action.

The immune system is affected by many conditions, substances, and reagents. The most commonly encountered are radiation, immunosuppressive drugs, bacteria, viruses, protozoa, other parasites, and some types of cancer. There are several genetic syndromes of immunodeficiency. Sometimes, immunodeficiency occurs due to other environmental reasons. For example, stress caused by loud noise, electric shock, separation of children from mothers, congestion, death of a spouse, or severe emotional or mental dysfunction may be related to immune abnormalities. When chemically induced immune dysfunction is evaluated, genetic and environmental factors should be carefully evaluated. Confirmatory reasons for immune regulation, particularly in humans, are diverse, so they must include emotional distress at least as a contributing factor.

Immune System Function in Bodies

The immune system is the body’s main defense against foreign bodies and biological agents (such as bacteria, viruses, chemical substances, foreign bodies, and tissues). The immune response involves the specific action of lymphocytes (a type of white blood cell) and is promoted by other white blood cells (including neutrophils, monocytes, macrophages, eosinophils, and basophils). The immune system can be seen as a system controlled by negative feedback.

The main component of this system is lymphatic tissue, which includes mature T (thymus) lymphocytes that mature through the development of the thymus and mature B lymphocytes that mature into the bone marrow. Each of these cell populations contains subtotals with different functions, specifically T cells (Toomey, 1982; Golub, 1987; Mangan, 1987). Some T cell populations play a role in enhancing or suppressing immune function. After exposure to immune system antigens, B cells differentiate into various plasma cells that differentiate to immunoglobulin (Paul, 1984; Miedema and Melliffe, 1985; Young and Geha, 1986).

Different Types of Immune System

The immune system is made up of lymphocytes and antibodies.


There are two types of lymphocytes.

T lymphocytes:

They identify and fight against antigens. Antigens can be any foreign body, such as microorganisms, foreign bodies during tissue transplantation. Therefore, T lymphocytes show a cell-mediated response.

B lymphocyte

They recognize antigens and form plasma cell cones. These plasma cells and cones synthesize released antibodies into plasma and tissue fluid. These antibodies attract the bacterial surface and accelerate phagocytosis. Sometimes, microorganisms produce toxins. Antibodies produce anti-toxins and neutralize these toxins. This is called a humeral immune response.

People have been vaccinated against specific diseases like polio, smallpox, measles and mumps. Therefore, people will in future produce antibodies against antigens and be immune to infection with this particular disease.

Antibody Proteins

Antibodies are special proteins called immunoglobulin’s. In response to antigens, vertebrates produce antibodies. An antigen or immunogenic is a foreign body (usually a protein) that stimulates the formation of antibodies.

Antibody fixes antigens. Eventually lead to antigen destruction. Antibodies are specific. These destroy the only antigen that stimulates the formation of that antigen. Antibodies are synthesized in B lymphocytes. They are then secreted into lymph and blood. They circulate freely in lymph and blood.

Antibody Structure Chain

The antibody molecule consists of four polypeptide chains: two identical light chains and two identical heavy chains. These chains are connected by disulfide bonds (S-S). Each chain of an antibody has two parts.

Variable amino acid sequence (V): These sequences determine which antigen will bind to a specific antibody.

Persistent amino acid sequence (C): In all antibodies of a class, these chains are identical.

Sometimes they are multiple copies of antigen molecules on the surface of foreign cells. As a result, large antigen-antibody complexes are formed.

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