35.4 Immune complex mediated diseases

Immune complex mediated diseases occur due to antibody reaction against either a self antigen or a non-self antigen. Such diseases are not restricted to a particular organ and are widely spread in the body. Serum sickness, Arthus reaction, polyarteritis nodosa, and poststreptococcal glomerulonephritis are some of the immune complex mediated diseases.

Serum sickness is an immunization of any individual with a non-self protein or foreign protein that leads to immune reaction.

Arthus reaction involves accumulation of antigen-antibody complexes in blood vessels.

Polyarteritis nodosa involves hepatitis B virus surface antigen which leads to vasculitis.

Poststreptococcal glomerulonephritis involves streptococcal cell wall antigen which leads to inflammation of kidney.

Immune complex mediated diseases may not be dangerous until the complexes are formed in very high amount and are not eliminated from the body. If such complexes tend to retain in blood vessels and capillaries, it may lead to their deposition followed by tissue injury.

 

35.5 T lymphocyte mediated diseases

T lymphocyte damages the tissue either by direct killing of the target cells or by inducing inflammation. In some of the cases T cell kills the target cells bearing the MHC class-I molecules. Inflammation is mainly induced by the subset of T cells, namely Th1 and Th17.