Cells of Immune System

Leukocytes

They are responsible for both specific and non specific immunity.

Leuko-white ; cytes- cells

They are originated from pluripotent stem cells in the liver

There are two types of leukocytes based on presence of nucleus.

Agranulocytes: cell without granules .It have two types

Monocytes, Lymphocytes

Monocytes

Single-cell,

Kidney shaped nucleus,

Produced in bone marrow,

The mature form of monocytes is called  Macrophage.

Monocytes – Circulate in the blood.

Macrophages –Circulate in the tissues.

Macrophage is useful to carry out Phagocytosis.

Lymphocytes

Divided into 3 types: T cell, B cell & NK cell

B lymphocytes or B cell - mature in bone marrow-circulates in the blood-reach to various lymphatic organs & Activated

This activated mature B cell is called Plasma cells.

Plasma cell secretes large quantity of glycoprotein which is called Antibodies.

T- lymphocytes or T- cell

It is produced in Thymus gland-circulate in the blood-reach to the lymphatic organs

It requires Specific antigen to bind

It do not secretes antibody

Activated T cell produced & secretes some proteins called Cytokines.

Natural Killer (NK) cells

They play important role in cell cytotoxicity.

 They also play important role in innate immune response

They are non-phagocytic cells

2. Granulocytes or Polymorphonuclear (PMN) Leukocytes

A group of white blood cells is collectively referred to  as granulocytes or Polymorphonuclear leukocytes (PMNs).

 Granulocytes are composed of three cell types as

Neutrophils, Eosinophils, Basophils.

These cells are important in the removal of bacteria and parasites from the body.

They engulf these foreign bodies and degrade them using their powerful enzymes.

Neutrophils

Neutrophils constitutes 50-70% of the circulating WBC’s.

 Life span 2-4 days in tissue.

They are first cell to arrive to the infection site.

It plays important role in inflammatory response.

Phagocytic and bactericidal.

Leucocytosis

Eosinophils

Eosinophil constitutes 1-3 % of the circulating WBC’s.

 Important in anti-parasite defences.

It presents Antigen to T cell in body.

 Release of contents present in Eosinophils can damage the parasite membrane.

 Eosinophils are associated with allergic diseases.

Basophils

Only present in the bloodstream, and represent <1% of circulating WBC.

They are non-Phagocytic cells.

 They play a major role in the allergic response.

They release their granules (containing histamine, serotonin, heparin, prostaglandin, etc into the bloodstream following exposure to specific allergens).

 When an individual is exposed to an allergen, specific IgE is produced. This IgE binds to the surface of basophils.

Mast cells

Mast cells are released from the bone marrow as undifferentiated precursor cells and do not differentiate until they enter the tissues (skin, connective tissue, mucosal epithelium, etc.)

Play a very important role in the development of allergic response.

They produce a variety of cytokines.

Dendritic cells

Originate in the bone marrow

 Function as antigen presenting cells (APC).

 Four types of dendritic cells are – Langerhan’s cells, Interstitial dendritic cells, Myeloid cells, Lymphoid dendritic cells.

                                                                                             

                                                                                 -Siddhi Shah