Lymphocyte

 

 Lymphocytes

Lymphocytes are small mononuclear agranular leukocytes.They are important part of body's immune system.

Shape and Size; smallest of leucocytes having diameter of 6-15 micrometer.

Lymphocytes have large single nuclei that occupy most of cell.

Most lymphocytes are found in the body's tissue especially in lymph nodes, spleen, thymus gland,tonsils and lymphoid tissue of gastrointestinal tract.

Lymphocytes are not phagocytes.

Lymphocytes originate from hemocytoblasts of bone marrow.

Migrate through blood

Invade lymphoid tissues where they establish colonies.

Produce additional lymphocytes

(Without involving the bone marrow)

Lymphocytes are part of our immune defense and act to recognize antigens, produce antibodies, and destroy cells that could cause damage.

Types of Lymphocytes

1. B lymphocytes

2. T lymphocytes

3. Natural killar cells(NK Cells)

1. B lymphocytes (B cells)

B lymphocytes originate in bone marrow and colonize typhoid tissue.

When B cells are activated they enlarge and become plasma cells.

B cells and their derivative plasma cells are source of specific immunoglobulin antibodies.

So they are involved in humoral immunity or circulating immune reactions.

2. T Lymphocytes

T lymphocytes mature in the thymus gland before they colonize typhoid tissue.

They function by directly attacking the infected or cancer cells.

T lymphocytes are identified with cell mediated immunity.

T cell are able to kill cells of the body that are infected by a virus.

T cells recognizes antigen on surface of cell infected with a virus enabling T cell to bind to and kill infected cell.

T cell are essential to immune response because they have unique "memory" system which allow them to remember past invaders and prevent disease when a similar invader is encountered again.

3. Natural killar cells (NK Cells)

NK cells are type of Lymphocytes and component of innate immune system.

They target tumor cells and protect against a wide variety of infectious microbes.

NK cells are already specialized to kill certain type of target cells, especially

1. Host cells that have become infected with virus.

2. Host cells that have become cancerous.

They are identified with natural or innate immunity, they bring about direct killing of microorganisms or Lysis of foreign material or body.

They do not need to recognize specific antigen before into action.

Lymphocytosis

Increase in number of Lymphocytes in blood.

Causes are-

1. Some acute viral infection, for example hepatitis

2. Some protozoa infection, for example; toxoplasmosis

3. Chronic bacteria l infection, example Tuberculosis

4. Some acute infection, for example; pertussis