Interactions Between Endogenous Glucocorticoids and Inflammatory Responses in Normal and Tumor-Bearing Mice: Role of T Cells

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Abstract
Appropriately stimulated lymphocytes and macrophages produce factors in vitro that increase serum corticosterone levels when injected in vivo. In this study, we used euthymic and congenially athymic mice on a BALB/c background to explore the role of T cells in controlling corticosterone levels and the leukocyte response to inflammation. Adult athymic mice had more intense inflammatory reactions than euthymic mice despite higher basal corticosterone levels. This latter condition may be due to interleukin-1 (IL-1) since macrophages from athymic mice when stimulated in vitro by lipopolysaccharide produced more IL-1 than macrophages from euthymic mice. In response to mitogen stimulation, however, splenocytes from athymic mice produced a factor (not IL-1), which, upon injection, increased corticosterone levels and suppressed inflammation. Production of this factor was enhanced by T cells since splenocyte supernatants from euthymic mice were more potent in eliciting both effects. Evidence for in vivo participation of T cells in regulating corticosterone levels was obtained by tumor transplantation. Injection of syngeneic tumor cells or cell-free tumorous ascites rapidly increased corticosterone levels in euthymic but not athymic mice. Anti-inflammation correlated with increased corticosterone levels but was observed also in athymic mice receiving syngeneic tumor transplants. These studies demonstrate that T cells enhance production of a lymphokine that increases corticosterone levels and are required for the corticosterone response to tumor transplantation. In addition, the data suggest two pathways of anti-inflammation in tumor-bearing hosts: a corticosterone-independent, T cell-independent mechanism and a T cell-dependent mechanism that involves a lymphokine-mediated increase in corticosterone blood levels.