In vitro effect of hydrocortisone on the attachment and ingestion phases of immunoglobulin G- and complement component 3b-mediated phagocytosis by human neutrophils

Abstract

The fluorescence quenching method (FQ method) was used to investigate the efect of hydrocortisone on the attachment and ingestion phases of immunoglobulin G (IgG)- and complement component 3b (C3b)-mediated phagocytosis by human neutrophils (PMNs). The results were compared with metabolic activity (O2- release) of the phagocytes. When the PMNs were treated with 5 x 10-5 M hydrocortisone or more, both IgG-mediated and C3b-mediated interactions decreased. The number of intracellular particles decreased as the total number of PMN-associated particles decreased, indicating an effect mainly on particle attachment. This was substantiated by the fact that pretreatment of the PMN with cytochalasin B resulted in a hydrocortisone dose-related decrease of interacting particles. The FQ method made it possible to quantify the stimulus-phagocyte interaction in relation to the metabolic response. Superoxide anion release decreased at the highest concentration of hydrocortisone used (5 x 10-3 M), which merely reflected the decreased number of interacting particles. No reduction in metabolic activation was obtained when the superoxide anion release was correlated with the number of interacting yeast-IgG particles. The results indicate that hydrocortisone primarily affects the binding capacity of Fc and C3b receptors, resulting in decreased metabolic activation. The effector functions, e.g., ingestion and metabolic activation, were not affected by hydrocortisone in this study.