Stressful stimulation of newborn mice increases the in vitro proliferative response in T cells from thymus.

The effects of prolonged stressful stimulation on the in vitro proliferative response of thymic T cells and the thymic zinc concentration were investigated in newborn Balb/c mice. Animals were stressed by intraperitoneal injections with aliquots from a heat-killed staphyloccocal suspension over one month. The splenic T lymphocytes from the stressed animals showed a significant reduction in the in vitro response to Concanavalin A (Con-A) stimulation. However, an unexpected and significant increase in proliferative response was observed when thymic lymphocytes from stressed animals were stimulated with the same mitogen. The intrathymic zinc levels were regularly elevated in stressed mice, in contrast to those values obtained in the thymus from healthy control mice. These results suggest that neonatal stress can disrupt the intrathymic maturation and the selection of pre-T lymphocytes. The increment of the in vitro proliferative response of T cells from the thymus of stressed mice may be caused by proportionally higher amounts of intrathymic lymphoid subpopulations expressing a mature phenotype and functionality.