agranulocytes

 

Based on presence or absence of granules leukocytes are two types-

1. Granulocytes:; 70-80%

2. Agranulocytes; 20-30%

20-30% of all WBCs are agranulocytes.

Agranulocytes are white blood cells that have no distinct granules in their cytoplasm.

Agranulocytes are two types- 

1. Monocytes, 6%

2. Lymphocytes, 25%

1. Monocytes

Monocytes are highly mobile phagocytes.Monocytes function mainly as phagocytic cells.

Shape and size;  Monocytes are mononuclear cells. They have larger, folded (kidneys or horse shoe shaped) single nucleus.

Monocytes are largest of WBCs 14-19 micrometer in diameter.

Monocytes are important in long term clean up of debris in an area of injury.

Monocytes normally remain in circulation for about 3 days, leave the circulation, become macrophages and migrate through various tissues.

Gather at site of infection or inflammation.

Which lines the vascular portion of the liver, lungs,lymph nodes, thymus gland and bone marrow.

Example, alveolar macrophages, spleen macrophages and puffer cells in liver.

Function of Monocytes

1. Healing and repair from site of vascular injury and infection.

2. Important role in immune system and immune response by processing specific antigen.

3. Host innate immunity against pathogen

4. Fight off bacteria, Viruses, and Fungi

5. Actively phagocytic

6. Fight against infection

7. Macrophages and monocytes phagocytize microorganism and cellular debris

8. Monocytes and macrophage in lung regulating immune response during homeostasis and inflammation.

9. Dendritic cells and Monocytes,

10.-Essential role in innate immunity

2. 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.

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

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.