Macrophage/T-lymphocyte interaction in the immune response to PPD in humans

The proliferative response of sensitized human T cells to low concentrations of purified protein derivative of tuberculin (PPD) in vitro has previously been shown to depend on the presence of autologous or HLA-D-compatible macrophages (M phi). In this paper we present evidence that the M phi/T cell interaction requires viable M phi and does not involve a soluble factor. T cells from neonates do not respond to PPD in our system, while M phi from neonates are able to present PPD to T cells from HLA-D matched sensitized adults. It is also demonstrated that the previously reported HLA-D restriction of T cell/M phi cooperation is not due to T cell mediated killing of allogeneic macrophages in vitro.