CLOSE RELATIONSHIP BETWEEN CYTOTOXIC LYMPHOCYTES-T GENERATED IN THE MIXED LYMPHOCYTE CULTURE AND INSULIN RECEPTOR-BEARING LYMPHOCYTES - ENRICHMENT BY DENSITY GRADIENT CENTRIFUGATION

In contrast to liver, fat, muscle, the fibroblast, and the monocyte, the lymphocyte does not bear insulin receptors unless it is activated by antigen or mitogen. Antigen stimulation by skin graft or in the mixed lymphocyte culture (MLC) generates a population of T lymphocytes, the effector function of which can be augmented by insulin. In the same pool of cells are found T lymphocytes with newly emergent insulin receptors capable of supporting this augmentation. This study demonstrates the close relationship between the augmentable effector T cell and the insulin receptor-bearing cell and strongly suggests that these cells are identical. Splenic lymphocytes from unidirectional murine MLCs were separated into light and heavy fractions by discrete density gradient eentrifugation daily and assayed for cellular-mediated cytotoxicity and for insulin receptors. Receptor-bearing and cytotoxic lymphocytes waxed and waned together primarily in the light fraction. Receptor-positive cells preceded effectors by 24 hr and the two characteristics were highly correlated over time (r ≥ 0.95). T-Cell depletion by specific antisera or by immunoabsorbent column chromatography demonstrated that most, but not all, receptor-bearing cells were T cells and that virtually all effectors were also receptor positive. When the insulin receptor was functionally removed from the lymphocyte membrane by trypsin proteolysis, effector function ceased. The return of cytotoxicity was accompanied by return of the lymphocyte insulin receptor. Receptor-bearing cells were predominantly of the Ly 2+3+ pedigree but Ly 1+ cells were also induced to bear the insulin receptor along with a few non-T cells. These data show that the emergence of a lymphocyte insulin receptor is not just a fortuitous marker event of cellular activation but provides a structure capable of supporting lymphocyte effector function. The appearance of Ly 1+ receptor-bearing cells suggests the alloactivation of T helpers and their participation in a T-T cooperative event. © 1979.