Hypothermia affects the phagocytic activity of rat peritoneal macrophages

To examine the effect of hypothermia on the phagocytic capacity of rat peri toneal macrophages for latex particles, male Wistar rats were exposed to 4 degrees C for 8 and 72 h. While the shorter exposure to cold did not affect body temperature and macrophage function, animals exposed to 4 degrees C f or 72 h showed a mean decrease of their body temperature by 1.5 degrees C. The superoxide anion production was significantly increased whereas the num ber of phagocytic cells decreased. In addition, the mean number of latex pa rticles engulfed by each individual cell was lower than that of controls. P eripheral blood mononuclear cells (PBMC) of these animals showed lower mito gen response to phytohaemagglutinin (PHA), while that for concanavalin A (C on-A) remained unchanged. Peritoneal macrophages exposed in vitro to 24 deg rees C for 60 min showed a decreased phagocytic capacity in comparison with macrophages kept at 37 degrees C, an observation suggesting the developmen t of an indigenous cell defect ior phagocytosis at lower temperatures. On t he other hand, the effect of additional humoral factor(s) on macrophage act ivity, such as an increase in serum level of catecholamines and corticoster one, cannot be excluded. The results of the study may contribute to underst anding the predisposition to infections during exposure to cold.