The acquired immunity has several other characteristics::
(1) It possesses memory in such a way that the system reacts more vigourously and more quickly on an antigen which it has met previously the first contact with the antigen leads to a small rise in serum antibodies (primary response) but subsequent exposure leads to a much larger increase in antibodies (secondary response) the basis of these responses is believed to be the formation of memory cells from both B-and T lymphocytes
(2) The immunity system shows tolerance in that it does not normally attack self material or in other words it is an induced specific unresponsiveness to substances that may induce sensitization in animals from soon after birth in an abnormal case the tolerance may not be seen as there may be production of antibodies against or sensitization by the products of the animals own tissues this is auto immunization or auto-sensitization various diseases resulting from autoimmunity are rheumatic fever glomerulonephritis myasthenia gravis lupus erythematosus etc
B and T Lymphocytes:
Lymphocytes are found in the lymphatic tissues such as lymph nodes spleen and lining of gastrointestinal tract (eg.tonsils peyers patches) There are always some lymphocytes circulating to and from blood and lymphatic system both the types of lymphocytes are originated from bone marrow stem cells the B- lymphocyte has been so named because such cells are matured in bursa of fabricius in birds in adult mammals they are directly derived from the bone marrow but they are matured under the influence of hormones produced by thymus hence the term T-lymphocytes in infancy the thymus is large and active but after puberty it undergoes atrophy
0 Comments