We propose to study the effect of the administration to human volunteers of cortisol or endotoxin or both on cytokine secretion by circulating mononuclear cells and neutrophils on expression of cytokine messenger RNAs in these cells, on the percentage of circulating T lymphocytes and T cell subsets and on the proliferative response of circulating lymphocytes to T cell mitogens. These investigations are designed to determine whether the administration of endotoxin or cortisol or both mimic the abnormalities of the immune response noted in seriously injured patients. We will also study the effect of the administration of growth hormone to patients with serious injury on the immunologic abnormalities customarily found in these individuals including altered cytokine production, decreased T cell activation and immunosuppressive serum. Finally, we will study the affect of the administration of low dose interleukin-2 and ibuprofen to seriously injured patients on resistance to infection, mortality and cytokine production, T cell activation and on the appearance of immunosuppressive serum.