Interleukin 6 primes human neutrophil and monocyte oxidative burst response

Interleukin 6 (IL-6), a 26-kDa inducible protein, is a cytokine with multiple biological activities. This paper reports on the regulatory role of rIL-6 on the function of human polymorphonuclear and mononuclear leukocytes, a property not described previously. rIL-6 by itself did not exhibit any chemotactic activity and it could not activate these cells for an oxidative burst response. Preincubation of both cell types with rIL-6 at concentrations of 5 and 50 ng/ml primed the cells for enhanced generation of oxygen radicals following stimulation with the chemotactic peptide f-Met-Leu-Phe or the phorbol ester PMA. The enhancement of the oxidative burst response occurred both at the level of superoxide anion generation, an early step in the activation pathway, and at the level of the hydrogen peroxide-myeloperoxidase mediated response, a later step in the oxidative burst pathway. The priming ability was abolished by heat treatment of rIL-6 at 100 degrees C but not at 70 degrees C. Stimulation of B cell growth and immunoglobulin production combined with enhancement of oxidative burst response of phagocytic cells by IL-6 provide an effective mechanism of fighting against invading micro-organisms.