An autologous mixed lymphocyte reaction was demonstrated between T and non-T lymphocytes. Sheep erythrocyte rosetting was used to separate human lymphocytes into T and non-T lymphoid preparations. Non-T lymphocytes stimulated the proliferation of autologous T lymphocytes. The cell in this preparation that was most stimulatory had the characteristics of a K lymphocyte. The allogeneic mixed lymphocyte reaction was also shown to reflect the proliferation of T lymphocytes stimulated by allogeneic non-T lymphocytes. Proliferation of T lymphocytes in the allogeneic mixed lymphocyte culture probably reflects a response to both foreign histocompatibility determinants and determinants present on non-T lymphocytes. It is suggested that the proliferative response of T lymphocytes to autologous non-T lymphocytes may be a step in the process by which T lymphocytes regulate immunity.

The magnitude and heterogeneity of the immune response to dinitrophenylated bovine gamma globulin was measured in aged and young mice at a cellular level using an inhibition of plaque-forming cell assay. The primary and secondary responses of 24-mo-old mice were markedly depressed in magnitude and restricted in avidity for the DNP determinant when compared to 2-mo-old animals. Bacterial lipopolysaccharide given at the time of immunization increased the restriction in heterogeneity seen in 12- and 24-mo-old mice. Indirect PFCs were more severely depressed than direct PFCs in 24-mo-old mice. Syngeneic, lethally irradiated, 2-mo-old mice reconstituted with aged spleen cells exhibit the depressed and restricted response to DNP-BGG seen in old mice. When 10(8) young thymus cells were given together with old spleen cells the heterogeneity of the response was increased. When 2-mo- and 24-mo-old spleen cells were transferred together into young recipients the magnitude of the response to the young spleen cells markedly reduced. Thus, there appears to be a loss of thymic-helper cells and an increase in suppressor activity in aged animals.

No abstract

No abstract

The basis for the age-associated defect in the response of lymphocytes to plant lectins has been studied. Using three independent assays we have shown that the number of mitogen-responsive cells is markedly reduced in lymphocyte preparations from old persons. In addition, studies using colchicine bloock and thymidine pulse techniques have revealed a failure of mitogen-responsive cells from old persons to expand into a proliferating pool of lymphocytes as is observed when lymphocytes from young persons are cultured with phytohemagglutinin. Thus, the impaired response of lymphocytes from old persons to mitogens is attributable to a reduced number of mitogen responsive cells and their failure to undergo clonal expansion.