Inhibitory Effects of Interleukin 6 on Immunity

Certain disease states are associated with abnormal increases in the monokine interleukin 6. Increased levels of interleukin 6 have been demonstrated in serum from patients with burns and are associated with systemic increases in endotoxin levels. Using a murine in vitro experimental model, we have studied the effects of interleukin 6 on various measures of immunity. Our data indicate that levels equivalent to the concentrations found in serum of burn victims inhibit T-cell proliferation. The inhibitory effect is dose and time dependent, is specific for T cells, is not due to impairment of interleukin 2 production or of interleukin 2 receptor expression, and is dependent on macrophages. These data suggest that extraordinary increases in interleukin 6 levels may be related to impaired T-cell responses and to an increased susceptibility to infection in the patient with burns.