Thymic involution in pregnant mice. II. Functional aspects of the remaining thymocytes

Non-specific immunological modifications in mice during syngeneic gestation can be demonstrated. A dramatic transient thymic involution results from a significant reduction in the subpopulations of the thymic cortex with the remaining thymocytes being mainly medullary in nature. Response to PHA and Con A is greatly reduced in this pool which can normally be strongly stimulated. No suppressor cells or alteration in thymic epithelial function could be demonstrated. The unexpected low responsiveness of the remaining thymocytes was reversible after in vitro neuraminidase treatment. Meanwhile, MRL of thymocytes to allogeneic cell during syngenic gestation was not impaired.