Are contact hypersensitivity cells cytotoxic?

Abstract

THYMUS-DERIVED lymphocytes (T cells), which participate in many regulatory and effector functions of the immune system, are divided into distinct subpopulations. Thus, T cells causing cell-mediated cytotoxicity can be distinguished from those cooperating with bone marrow-derived lymphocytes (B cells) in the humoral response^1–3. Cytotoxic T cells also seem to be distinct from the cells responsible for the mixed lymphocyte and graft versus host reactions^4,5. Furthermore, T-cell subpopulations can interact with each other to augment various cell-mediated immune responses^6–8. We have investigated whether the T cells causing contact sensitivity belong to a different subset from those causing cell-mediated cytotoxicity. Our studies were based on two observations: first, that in mice contact sensitivity to the trinitrophenyl group (TNP) can be transferred adoptively by spleen or lymph node cells of sensitised animals; and, second, that cytotoxic T cells able to lyse TNP-coupled target cells can be induced in vitro^11–13. We have found that contact sensitivity cells fail to display cytotoxicity, while cytotoxic cells fail to transfer contact sensitivity. From this we conclude that these two functions are performed by distinct T cell subpopulations.