Macrophage‐Dependent Response of Immune Human T Lymphocytes to PPD In Vitro Influence of HLA‐D Histocompatibility

The proliferative response of immune human T lymphocytes to low concentrations of purified protein derivative (PPD) in vitro was found to require the presence of macrophages. By coculturing different combinations of immune T lymphocytes and allogeneic macrophages with PPD in low concentration, optimal stimulation (that is, as efficient as the autologous combinations) was shown to require HLA-D identity between the macrophages and responding T cells. Identity for HLA-A and -B appeared to be of less or no importance. It is concluded that membrane structures encoded by HLA-D or closely linked loci are involved in the human macrophage/T-lymphocyte interaction in the proliferative response to PPD, much in the same way as the Ia antigens of rodents.