The involvement of T1 and T2 lymphocytes in primary and secondary delayed type hypersensitivity responsiveness.

The contribution of short-lived and long-lived T lymphocytes (T1 and T2 lymphocytes respectively) to primary and secondary delayed type hypersensitivity (DTH) responsiveness was studied by means of thymectomy of adult mice (ATx) with sheep red blood cells as the antigen. Within one month after ATx a fall of the primary and secondary DTH responsiveness was found of 20% and 50% respectively. This reduction can be attributed to the loss of short-lived T cells. ATx 8 months prior to the administration of the priming dose caused a decrease of the primary and the secondary DTH responsiveness of about 50% and 65% respectively. These data suggest that both the short-lived T1 and the long-lived T2 precursor cells account for the occurrence of (1) cells mediating the primary DTH response and (2) memory cells responsible for the secondary DTH response. The contribution of both populations of precursor cells in primary and secondary DTH responsiveness appeared to be only proportionally different.