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TULSI PRAJNA
lex as well as mysterions in their particular. It is defined, in terms of functions, as a resistance to all types of external invasions The condition of insusceptibility to disease. due to the presence, in blood and tissues, of substances that inhibit development of the infection and owing to a change in the ability of the body cell to react against the causative agent is called immunity. These substances are known as antibodies or immune bodies. When immune bodies are present in the body at birth the condition is known as congenital or inherited immunity. Accumulation of antibodies which provides nonspecific denfense against all foreign invaders the condition is called acquired immunity. The first line of immunity are the skin, enzymes etc. The second line of defense is within the blood in the form of white blood cells (WBC), lysosomes, polypeptides etc. WBC popularly known as lymphocytes because they concentrate themselves in lymph of body and are mobile units to destroy the foreign invaders inside the blood itself.
There are 6000 to 8000 W BC per cubic mm of blood in a human adult. An increase in their number is known as leucocytosis, which is a characterstic of a number of pathological conditions but it may also be encounted within a healthy individual, WBC are of five types- neutrophils (60-70%), Eosinophils (2-4 %), Basophils (0.5-1%), Lymphocytes (20-25%) and Monocytes (3.8%). In the process of immunity it is mainly ncutrophils and monocytes that destroy invading bacteria, virus and other toxins. The neutrophils are the mature cells that attack and destroy the bacteria and virus in the circulating blood, while monocytes are immature cells and have less ability to destroy the pathogens in blood. When they reach to the injured tissues they are being activated, to be converted into macrophages to combat pathogens at the site.
Acquired or adaptive immunity is the ability of the body to defend itself against specific invading agents such as bacteria, virus, toxins and some other foreign tissues. It consists of two closely allied immune responses. In the one process of response formation of specially sensitized lymphocytes takes place that have the capacity to attack on to the foreign agent and destroy it. This is called celluler (T-cell mediated) immunity. It is particularly effective against fungi, parasites, intracellular viral infections, cancer cells and foreign tissue transplants. In other response body produces circulating antibodies that are capable of attacking on invading agents. This is called humoral (antibody mediated) (B-cell) immunity. Cellular and humoral immunity are the product of the body's lymphoid tissue. The placement of lymphoid tissue is stratigically designed to intercept ad
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