Different rules govern help for cytotoxic T cells and B cells

Abstract

RECENT experiments with radiation chimaeras^1,2 indicate that T cells differentiating in an H–2D compatible, but H–2I different, thymic environment are completely unresponsive to vaccinia virus. The explanation favoured² for this surprising finding is that participation of helper T cells³ (TH) is an absolute requirement for the generation of virus-immune cytotoxic T cells (Tc). No response is seen because the TH populations are ‘locked in’ to recognising the spectrum of H–2I antigens presented on radiation-resistant thymic cells². They cannot, therefore, interact with the Tc precursors which are genetically different in the I region. The result is a total failure of responsiveness. We report here that we have tested this concept further by stimulating acutely tolerised^4,5 T-cell populations in H–2I different, but H–2D compatible virus-infected recipients. Our results indicate that there is apparently no need for participation of TH populations restricted to the H–2I region specificities expressed in the recipient environment. This differs from the situation for TH–B-cell collaboration^4,5, and suggests that help for the Tc response operates directly between T-cell subsets.