Ontogeny of Cell-Mediated Immunity of Murine Thymocytes and Spleen Cells: In vitro Mixed Leukocyte Culture and Cell-Mediated Lympholysis Reactions

Abstract

The ontogeny of cell-mediated immunity of spleen cells and thymocytes from B10 mice was studied in both in vitro mixed leukocyte culture and cell-mediated lympholysis reactions. Results show that newborn spleens contain cells competent to respond to X-irradiated allogeneic spleen cells in mixed leukocyte culture. The mixed leukocyte culture response of spleen cells, in terms of both index of stimulation and increment of tritiated thymidine incorporation, seems to be higher for mice four weeks or older than for mice less than four weeks old. The cell-mediated lympholysis response of spleen cells is not detectable until two days postpartum. It reaches adult levels in terms of % cytolysis by day four after birth. Thus, the transition period of the ontogeny of cell-mediated lympholysis response of spleen cells is apparently 0–4 days of age. Newborn and early postnatal thymocytes (0–7 days of age) respond in mixed leukocyte culture at least as strongly as adult thymocytes (2–3 months of age). The cell-mediated lympholysis response of thymocytes is already detectable at birth, but weaker in terms of % cytolysis when compared with the cell-mediated lympholysis response of thymocytes from two days to six weeks of age. The cell-mediated lympholysis response of thymocytes starts to decline at 6–8 weeks of age. Thus, around the time of birth, there is a transition period in the cell-mediated lympholysis response of thymocytes during which thymocytes start to show high cell-mediated lympholysis reactivity. There is a second transition period between six and eight weeks of age during which the cell-mediated lympholysis response of thymocytes diminishes. The early, as well as late, postnatal cell-mediated lympholysis response of both spleen cells and thymocytes seems to be specific in nature.