Strong HLA-DR expression in T cell cultures after activation is necessary for IL-2-dependent proliferation

We have examined the appearance of DR antigens on human T cells activated by PHA, using a monoclonal anti-DR framework antibody and a large panel of human HLA typing sera. Strong DR expression within the culture by day 8 was associated with the ability of cells to grow for long periods in IL-2 containing medium, whereas weak or absent DR expression was predictive of poor in vitro growth. All the cells responded equivalently to initial stimulation with PHA. These data support the hypothesis proposed by Moretta et al. to explain blocking of IL-2-dependent proliferation by an anti-DR antibody--that DR molecules may be involved in the transmission of signals by IL-2.