The effect of mild hyperthermia on the morphology and function of murine resident peritoneal macrophages

During short term culture of murine resident peritoneal macrophages, increasing the temperature from 37 to 39 degrees C resulted in an increased activity of several surface receptors (FcR and receptor for gluteraldehyde-fixed sheep red blood cells), enhanced phagocytosis of yeast particles, improved spreading, and an accelerated reduction of nitroblue tetrazolium. At 41 degrees C, however, significant reduction of several functional properties (endocytosis of colloidal gold and horseradish peroxidase, phagocytosis of yeast particles) and a decrease in the reduction of nitroblue tetrazolium, the incorporation of tritiated uridine, and Fc and C3b surface receptor activity were observed. In addition morphological evidence of apoptosis, observed in a small number of cells cultured at 39 degrees C and in the majority of macrophages maintained at 41 degrees C, was confirmed by DNA electrophoresis. The data indicates that a reduction of several functional activities of macrophages occurs at 41 degrees C and apoptosis may largely account for these effects.