Cloned helper T cells display parallel specificities by in vitro proliferation and in vivo generation of delayed type hypersensitivity

We have been studying mechanisms of graft rejection. DTH is a proposed mechanism of graft rejection classically described as being mediated by helper T cells and effected through activated macrophages. We used cloned helper T cells as the population of sensitized cells in the murine footpad assay to initiate DTH. We sought to establish the specificity of the DTH reaction using cloned helper T cells and to compare the in vivo and in vitro specificity of these cells. Our previous work and this series of experiments demonstrate the following: 1. Cloned helper T cells alone do not proliferate in vitro or generate DTH in vivo. 2. These particular cloned helper T cells require antigenic stimulus in order to proliferate in vitro and to initiate DTH in vivo. 3. The specificity of the in vitro proliferative response predicts for the specificity of the DTH response. 4. 1 to 3 above suggest that proliferation may be an integral component of DTH. Therefore, factors that stimulate T lymphocyte proliferation may also initiate a DTH reaction. Likewise, factors that inhibit proliferation may also inhibit DTH. This has implications for immunosuppressive therapy. 5. The initiation of DTH in the murine footpad assay using cloned helper T cells is a specific immune reaction that occurs in response to allogenic splenocytes and cross-reactive splenocytes but not in response to syngeneic or unrelated third-party splenocyte antigens.