CYTOKINE CONTROL OF PMN PHAGOCYTOSIS - REGULATORY EFFECTS OF HYPOXEMIA AND HYPOXEMIA-REOXYGENATION

We investigated the effects of hypoxemia and hypoxemia-reoxygenation ( H/R) on interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-alpha), or IL-1 beta stimulation of whole blood polymorphonuclear leukocyte ( PMN) phagocytosis and bactericidal activity. Whole blood PMN were rend ered hypoxemic (venous PO2 < 15 mmHg), normoxic (venous PO2 60-80 mmHg ), or reoxygenated after hypoxemia (H/R = venous PO2 150-200 mmHg) and were incubated with IL-8, TNF-alpha, or IL-1 beta before sequential a ddition of serum-opsonized fluorescent microspheres and fluorescein is othiocyanate-conjugated mouse anti-human CD64, CD32w, CD16, CD35, or C D11b/CD18. Concomitant two-color flow cytometric analyses were then pe rformed measuring mean channel fluorescence and the percentage of PMN positive for phagocytosis, with simultaneous subset receptor analysis on populations of PMN that exceeded control levels of phagocytosis. Du ring hypoxemia, whole blood PMN phagocytosis in the presence of IL-8, TNF-alpha, or IL-1 beta was increased compared with normoxia. Northern blot analyses revealed an increase in steady-state mRNA levels for CD 32w during hypoxemia + IL-8 and CD64 during hypoxemia + IL-1 beta. Dur ing reoxygenation, both whole blood PMN phagocytosis and bactericidal activity were reduced in the presence of IL-8, TNF-alpha, or IL-1 beta , and in subsets of PMN with reduced phagocytosis H/R reduced CD64, CD 32w, CD16, CD35, and CD11b/CD18 expression in the presence of each cyt okine. Northern blot analyses revealed that H/R reduced mRNA levels fo r opsonic receptors primarily for IL-1 beta-stimulated PMN. These resu lts demonstrate a direct regulatory effect of hypoxemia and H/R on who le blood PMN phagocytosis, receptor expression, and steady-state mRNA levels of both Fc(gamma) and complement receptors.