612 INHIBITION OF NEUTROPHIL PHAGOCYTOSIS BY HYDROCORTISONE IN VITRO

Abstract

Inhibition of several membrane-associated neutrophil (PMN) functions by corticosteroids has been suggested in previous reports. We evaluated the effect of hydrocortisone (HC) on phagocytosis by human PMNs with two widely utilized phagocytic assays. PMNs of adult volunteers were obtained by methylcellulose-hypaque separation. After a 30-minute pre-incubation with varying concentrations of HC, the cells were assayed either by Stoessel's Oil Red O method or by Tan's phagocytic-bactericidal method. Simultaneous control PMNs were pre-incubated with drug-free buffer. Trypan blue viability was satisfactory (> 93%) with up to 2 × 10-3M HC. Phagocytosis and bactericidal activity toward Staphylococcus aureus were unperturbed using up to 2 × 10-3M HC. By contrast, in the Oil Red O assay a significant inhibition of phagocytosis was observed with 2 × 10-3M HC (mean % inhibition ± SE 14.5 ± 1.6) and with 2 × 10-4M HC (17.9 ± 4.2, p < 0.025). With 2 × 10-2M HC profound inhibition of phagocytosis (76.1±5.1) occurred; similar inhibition (60 ± 12.5) was observed in the phagocytic-bactericidal assay. At 2 × 10-2M concentration, however, HC caused severe morphological cell alterations with over 60% of the PMNs trypan blue positive. Bactericidal activity remained normal at any HC concentration. Our data indicate that 1) in vitro exposure to HC affects phagocytosis by PMNs 2) it does not impair bactericidal activity 3) the Oil Red O phagocytic assay is more sensitive than the phagocytic-bactericidal test in detecting moderate phagocytic defects.