HLA-D restriction of the macrophage-dependent response of immune human T lymphocytes to PPD in vitro: inhibition by anti-HLA-DR antisera.

The response of T cells from sensitized individuals to low doses of PPD in vitro is macrophage-dependent. By testing different allogeneic combinations of macrophages and T lymphocytes, it was found that an optimal response required that antigen be presented by macrophages sharing at least one of the HLA-D determinants of the T cell donor. Antisera recognizing HLA-A, -B or -DR antigens were found to be able to inhibit this proliferative response. The anti-HLA-DR antisera were found to exert their inhibitory effect only when directed towards an antigen shared by the donors of the T lymphocytes and the macrophages. Anti-HLA-A and -B sera, however, had an inhibitory effect when reactive with the responding T lymphocytes, irrespective of their reactivity with the cooperating macrophages. It is concluded that an optimal secondary response of in-vivo-immunized T lymphocytes to PPD requires the combined recognition of the antigen and 'self' membrane structures encoded by the HLA-D locus.