Gamma interferon is not essential in host defense against disseminated candidiasis in mice

Apoptosis is well known to be mediated by oxidative stress. To evaluate the functional role of reactive oxygen intermediates (ROI) produced by neutrophils, we compared the rates of apoptosis in neutrophils isolated from normal donors and from patients with chronic granulomatous disease (CGD), a hereditary defect in ROI production. Spontaneous cell death in CGD neutrophils in vitro was significantly inhibited relative to normal neutrophils. The acceleration of apoptosis induced by anti-Fas monoclonal antibody (MoAb) in CGD neutrophils was much slower than that seen in normal neutrophils. These findings suggest that the apoptosis of neutrophils may be mediated by endogenous oxidative products. This suggestion was confirmed by observation that apoptosis of normal neutrophils was markedly inhibited by reduction of intracellular levels of hydrogen peroxide (H2O2). The inhibition of apoptosis in normal neutrophils by adding catalase occurred regardless of the presence of anti-Fas MoAb. H2O2 increased both spontaneous apoptosis and Fas-mediated apoptosis of the CGD neutrophils in proportion to that seen in normal neutrophils. Although several factors that mediate the apoptosis of neutrophils remain to be determined, these results suggest that ROI are major mediators of the apoptosis in neutrophils and may be involved in Fas-mediated signal transduction pathway.     

Expression and release of the monocyte lipopolysaccharide receptor antigen CD14 are suppressed by glucocorticoids in vivo and in vitro

The effect of glucocorticoid (GC) treatment on expression and release of the monocyte cell surface LPS receptor Ag CD14 was studied in vivo and in vitro. In patients with acute inflammatory diseases receiving GC pulse therapy serum concentrations of soluble CD14 and CD14 expression by peripheral blood monocytes decreased significantly. The LPS-binding capacity correlated positively with the amount of cell surface CD14 by human blood monocytes. In vitro, a time- and dose-dependent effect of GC preparations on monocyte membrane and soluble CD14 by cultured peripheral blood monocytes was found. Incubation with 2 x 10(-8) M prednisolone down-regulated cell surface CD14 after 72 h, and 2 x 10(-7) M suppressed CD14 expression even after 24 h. Prednisolone also decreased release of the soluble CD14 Ag, where a 10-fold higher GC concentration was required for a significant suppression compared with membrane CD14 during culture. Expression of other monocyte membrane Ags were either unchanged (CD33, CD35), diminished (CD13, CD89), or increased (CD32) by GC, indicating no general down-modulation of cell surface Ag expression. Preincubation with glucocorticoids for 24 h significantly down-regulated CD14 expression during subsequent steroid-free culture for at least 7 days. In cultured monocytes, the LPS-induced increase of membrane and soluble CD14 was markedly but not completely inhibited by prednisolone. Therefore, GC treatment suppresses the up-regulation of the LPS receptor during endotoxin challenge, and likewise, the IL-1 secretion after LPS stimulus was significantly diminished. Taken together, the suppression of the monocytic cell surface and soluble endotoxin receptor CD14 by GC may contribute to the increased risk of infections in patients undergoing steroid therapy.