Paradoxical presence of T cell anergy during successful T cell-dependent tumour immunotherapy: characterization of a state of T cell 'amnaesia' following systemic administration of C. parvum.

Systemic administration of Corynebacterium parvum causes T cell-dependent regression of an established methylcholanthrene-induced murine fibrosarcoma beginning 10 days after Cp injection. At this time, tumour specific effector T cell responses measured by reactivity in a T helper cell assay or in a Winn assay disappear only to return later. We refer to this temporary lapse in T cell reactivity as immunological 'amnaesia'. Antigen specific T cell responses within all lymphoid organs appear to be affected. The 'amnaesic' state is characterised by the presence of primed T cells but the absence of T effector cells and suppressor cells. The differentiation of the primed T cells is blocked probably as a result on the non-delivery of a differentiation signal. There are several possible mechanisms which could account for this; the one we prefer is that cells are prevented from entering T cell-dependent cell interaction areas within lymphoid organs. This state of T cell 'amnaesia' may underlie anergy in some inflammatory, infectious and neoplastic diseases. The apparent paradox of T cell-dependent tumour regression occurring in mice with depressed T cell responses is discussed.