Abstract
Ia [immune response associated] antigens are rapidly secreted by a subpopulation of splenic T [thymus-derived] lymphocytes which are nonadherent and which express the surface phenotype Ly-1+, Ly-2- and Ia-. Secretion of the Ia antigens was a metabolically active process which was inhibited by sodium azide and by Pactamycin, an inhibitor of protein synthesis.