Mechanisms of the adjuvant effect of hemoglobin in experimental peritonitis. VI. Effects of stroma-free hemoglobin and red blood cell stroma on mortality and neutrophil function

Abstract

Hemoglobin is known to increase the lethality of experimental E. coli peritonitis, but its mechanism of action has not been defined. Some evidence from this laboratory previously suggested that hemoglobin could interfere with local leukocyte function in the peritoneal cavity. In the present study we compared the effect of impure bovine hemoglobin, highly purified stroma-free hemoglobin, and red blood cell stroma on the mortality rate of rats with Escherichia coli peritonitis, as well as on human neutrophil function in vitro. Both hemoglobin preparations markedly increased the mortality rate at low bacterial concentrations. Red blood cell stromal elements increased the rate to a minimal degree and only at high bacterial concentrations. The character of the E. coli-induced peritoneal leukocytosis was not significantly affected by concomitant administration of either stroma-free hemoglobin or red blood cell stroma. Although crystalline bovine hemoglobin inhibited in vitro leukocyte chemotaxis, centrifugation of this preparation to remove debris abrogated this effect. Stroma-free hemoglobin had no effect on in vitro leukocyte chemotaxis. Red blood cell stromal elements in high concentration diminished phagocytosis and bacterial killing by human neutrophils, but stroma-free hemoglobin had no effect on these neutrophil functions. The results confirm that hemoglobin is a potent adjuvant in experimental E. coli peritonitis, but contrary to our previous conclusion does not owe this effect to direct interference either with neutrophil influx into the peritoneal cavity during bacterial peritonitis or with human leukocyte function in vitro. Such prior conclusions appear to have been based on insoluble material including stromal elements in the hemoglobin preparations used. Red cell stromal elements derived from as little as 1 ml of packed red cells can significantly interfere with the phagocytosis and killing of E. coli.