Evidence for an abnormal microenvironment in the thymus of New Zealand black mice.

The proliferative response of NZB and DBA/2 thymocytes and spleen cells to allogeneic cells and mitogens was studied in intact and lethally irradiated bone marrow-repopulated syngeneic recipients. The major findings were complete recovery of function in NZB spleen cells and premature recovery in thymocytes compared to the control DBA/2 strain. This recovery was not influenced by the administration of thymosin to the recipients, and was not due to functional thymocytes present in the donor marrow inoculum. These results suggest normal or increased support of T cell differentiation by the radioresistant thymus in 4-month-old NZB mice. Thymic epithelial cell products regulating T cell maturation may be disordered or unbalanced but do not appear to be broadly deficient at this age.