Lymphocytes are associated with the protection of the body against foreign material. There are 2 types of lymphocytes that function. They are,
B - lymphocytes.
These are found in lymph node and spleen.
Antigens are foreign bodies such as bacteria, virus or any toxin that enters the body.
The T-lymphocytes produce a number of chemical substances that act against antigens such as viruses, pollen, fungi and bacteria.
The B - lymphocytes produce antibodies that ingests the foreign particles.
Active Immunity : Here the individual responds to an antigen and produces antibodies specific to one microbe. This can be natural or artificial.
Passive Immunity : Here the individual is given antibodies produced by someone else. The readymade antibodies are injected into the infected person.
This condition is caused by the human immune deficiency virus (HIV). HIV acts mainly on T - lymphocytes. When they are infected their number is reduced, causing suppression of T-cell immunity leading to infections such as pneumonia, tuberculosis and malignant tumors.
They are also called as W.B.C or Leucocytes These are transparent, not coloured and fewer than the red cells possessing nucleus. There are 8,000 W.B..C. in each cubic millimeter of blood.
(a) Granular Leucocytes which includes Neutrophils, Eosinophils and Basophils.
(b) Agranular Leucocytes consists of lymphocytes and monocytes cells.
Granulocytes and monocytes play a vital role in protecting the body from micro organisms. By their power of amoeboid movement they can move freely in and out of the blood vessels and wander about in all parts of the body. They surround any area which is infected or injured and fight against the organisms, by ingesting them by the process of phagocytosis. Lymphocytes make antibodies to protect against chronic infection and to maintain immunity to infections.
Inflammation is a series of changes in tissues in response to injury. When injury occurs due to bacteria, trauma, chemicals, heat or any other substance, several substances are released that cause local swelling around the injured area. The neutrophils also migrate to this area in increased number. They are phagocytic in action. Similarly the macrophages are released which have greater phagocytic action.