Effects of hyperthermia on phagocytosis and intracellular killing of Sporothrix schenckii by polymorphonuclear leukocytes.

The effects of hyperthermia on phagocytosis and killing of Sporothrix schenckii by polymorphonuclear leukocytes (PMNs) were investigated in order to clarify the mechanism of local thermotherapy for sporotrichosis. Yeast cells of S. schenckii, PMNs and serum were incubated at 37 degrees C or 40 degrees C for 2 or 4 hours. Rate of phagocytosis and killing rate (rate of germination) were estimated, and their processes were observed by transmission electron microscopy. There was no effect of hyperthermia on the phagocytosis rate, but the killing rate increased significantly at 40 degrees C. Electron microscopic examination showed an increase of granularity in the yeast cytoplasm, elongation and fragmentation of the cell membrane. The ultrastructural changes were basically identical under both temperatures, but the degree of these changes was higher at 40 degrees C than at 37 degrees C. Although both intact and degenerated yeasts were found in the same conditions, their transient forms were few, suggesting that the PMN-killing process was completed promptly.