Ontogenesis of the in Vitro Response of Murine Lymphoid Cells to Cellular Antigens and Phytomitogens

Abstract

The ontogenesis of cellular immunity in CBA/J mice was studied by using in vitro culture of spleen and thymus cells from donors varying in age from 2 to 70 days. Cell suspensions were assayed for reactivity in the mixed lymphocyte interaction (MLI) and isogeneic lymphocyte interaction (ILI) and for responsiveness to phytohemagglutinin (PHA) and pokeweed mitogen (PWM). The capacity of spleen cells to participate in the MLI and ILI and to respond to PWM appeared at an earlier age than did PHA responsiveness. The refractoriness of neonatal spleen cells to PHA stimulation could not be overcome by varying the number of cells or the quantity of PHA used in each culture. The thymus of neonates was found to have a similar selective deficiency of PHA-reactive cells. Cells responsive to PHA could not be detected in the neonatal thymus even after treatment of cell donors with cortisone acetate, although similar treatment of adult donors dramatically enhanced thymic cell responsiveness to PHA. These studies suggest that PHA responsiveness either requires a separate lymphoid cell population or reflects a later stage of lymphocyte maturation than the other in vitro activities assayed in this investigation.