Thymic involution in pregnant mice. I. Characterization of the remaining thymocyte subpopulations

Pregnancy-induced thymic atrophy was studied in mice during the course of syngeneic gestation and the post-partum period. Cortical thymocytes were greatly reduced in number as shown by the binding of fluorescein-labelled PNA. The pool of steroid-resistant (SR) medullary thymocytes appeared unchanged in pregnant mice when studied by means of a specific heteroantiserum (SRCA). Therefore, in pregnant mice, these two surface markers demonstrated that thymic atrophy was linked to steroid-sensitive (SS) cortical cell reduction. The presumed hydrocortisone resistance of the mother's remaining thymocytes is not related to a difference in the number of steroid receptors as determined by 3H-dexamethasone binding.