Effects of temperature on phagocytosis of human and calf polymorphonuclear leukocytes

The in vitro effect of temperature on the phagocytic function of human and calf polymorphonuclear leukocytes (PMN) was studied. To observe the PMN phagocytic function (PPF) at various temperatures, PMN from healthy human and calf donors were incubated with serum-opsonized fluorescent latex particles (diameter 1.66 microns) at 25, 37, 40, 42, 44, or 46 degrees C for 1 h and then observed for their phagocytic activity by fluorescent microscopy. At 25, 40, and 42 degrees C, human PPF was not significantly different from that at 37 degrees C (87%, 89%, and 80% vs. 93%). At 44 degrees C, PPF was noticeably depressed (19%, p < 0.05) when compared to that at 37 degrees C. Next, to determine the critical temperature and duration of exposure that would irreversibly damage PPF, PMN were preincubated at 42, 44, or 46 degrees C for 5-30 min before being subjected to a standard phagocytosis assay at 37 degrees C. The human PPF was significantly depressed after 30 min at 44 degrees C (33%, p < 0.05) or 10 min at 46 degrees C (30%, p < 0.05). In conclusion, neither human nor calf PPF was significantly altered at and below 42 degrees C. In contrast, the PPF was irreversibly and time-dependently damaged when incubated at and above 44 degrees C.