Because antigen receptor genes are randomly rearranged, some immature lymphocytes produce receptors specific for epitopes on the organism’s own molecules. why doesn’t the immune system attack these molecules on the body’s cells and tissues?

Since antigen receptor qualities are haphazardly reworked, some juvenile lymphocytes deliver receptors particular for epitopes on the life form's own particular atoms. On the off chance that these self-receptive lymphocytes were not killed or inactivated, the safe framework couldn't separate self from non-self and would assault body proteins, cells, and tissues. Rather, as lymphocytes develop in the bone marrow or thymus, their antigen receptors are tried for self-reactivity. Some B and T cells with receptors particular for the body's own particular atoms are wrecked by apoptosis. The staying self-receptive lymphocytes are normally rendered nonfunctional, leaving just those that respond to outside particles.