Corticosteroids, serum, and phagocytosis: in vitro and in vivo studies

The phagocytic-bactericidal capacity (PBC) of human polymorphonuclear leukocytes (PMNs) for strains of Klebsiella (K) and of Enterococcus (E) was unaffected in vitro by the presence of 100 mug of either hydrocortisone (HC) or of methylprednisolone (MP) per ml in the medium. At higher concentrations (500 to 2,000 mug/ml) both compounds impaired PBC-K and PBC-E, but the latter was less sensitive to steroid-induced inhibition. In addition to interfering with intracellular killing of both organisms by PMNs, 2,000 mug of HC per ml also inhibited ingestion of E, although not of K. Steroid-induced inhibition of PBC-K in vitro was completely abolished by increasing the concentration of serum used as opsonin. The PBC-K of human PMNs obtained 30 min after intravenous injection of 1 g of MP was unimpaired in vitro in the presence of 10 to 90% simultaneously obtained autologous serum containing 42 mug of MP per ml. These findings suggest that short-term, high-dosage administration of MP is unlikely to produce clinically significant impairment of intraleukocytic bacterial killing.