Immune Cells and it's Function

 Immune Cells and it's Function

 "A protective or defense reaction against foreign substances. These foreign substances, known as antigens, release from the surface of the lymphocytes, the signals for cellular or humoral immune response."

The immune defense mechanism of the body involves the action of white blood cells, or leukocytes. Leukocytes include neutrophils, eosinophils, basophils and monocytes, all of which are phagocytic, as well as two types of lymphocyte (T-cells & B-cells), which are not phagocytics. but are critical to the specific immune response and the humoral response.


After their origin in the bone marrow, T-cells migrate to the thymus (hence the designation "T"), a gland just above heart. There they develop the ability to identify micro-organisms' and virus by the antigens exposed on their surfaces. Tens of millions of different T-cells are made, each specialized in the recognition of one particular antigen. No invader can escape being recognized by at least a few T-cells. There are four principal kinds of T-cells.

(A) Helper T-cells (Th) : Commander of the immune response, detects infection and sounds the alarm, initiating both T-cell & B-cell responses.

(B) Inducer T-cells :
immediate response to infection, mediates the maturation of other T-cells in the thymus i.e. oversce the development of T-cells in thynus.

(C) Cytotoxic T-cells (Tc):
(cells-poisoning) Detects and kill infected body cells, recruited by helper T-cells.

(D) Suppressor T-cells :
They terminate the immune response. Dampen the activity of T and B- cells, scaling back the defense after the infection has been checked.


Unlike T-cells, B-cells do not travel to thymus, they complete their maturation in bone marrow (B-cells are so named because they were originally characterized in a region of chickens called the bursa). From the bone marrow, B-cells are released to circulate in the blood and lymph. Individual B-cells, like T-cells, are specialized to recognise particular foreign antigen. When a B-cell encounters the antigen to which it is targeted, it begins to divide rapidly, and its progeney differentiate into plasma cells and memory cells,

Plasma cells

Biochemical factors devote to the production of antibodies (proteins) directed against specific foreign substance. Antibodies produced stick like flags to that antigen where ever it occurs in the body, making any cell bearing the antigen for destruction. The immunity that Pasteur observed resulted from, such antibodies and from the continued presence of the B-cells that produced them.

The humoral immune response, carried out by B-cells, protects the body from bacteria and other invading cells, by labeling these cells for destruction.

The B-cell lymphocytes that carry out this response produce and secrete antibodies that circulate in the blood plasma, lymph and other extracellular fluids, hence the term HUMORAL (relating to fluid) is used in describing their immune responses. In response to antigen exposure, a B-cell divides to produce plasma cells that serve as short lived antibody factories, and to produce long-lived memory cells.

Mast cells

Initiator of the inflammatory response, which aids the arrival of leukocytes, at a site of infection, secrete histamine and are important in allergic responses.

Monocyte : Precursor of macrophage.

Macrophage :
The body's first cellular line of   defense, also serves as
antigen-presenting cell to B & T-cells  engulfs antibody covered cells.

Killer cells

They recognise and kill infected body cells, natural killer cells (NK) detect and kill cells infected by a broad range of invaders, killer (K) cells attack only antibody coated cells.

(Above mentioned are various type of cells of the Immune system).

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