Leucocidin

LEUCOCIDIN, a substance produced by staphylococci that kills white blood cells. It was discovered by Van de Velde in the pleural exudate of rabbits caused by gonococci. L. is destroyed by heating to 57°. It is also found in artificial cultures. Under the action of L., white blood cells undergo vacuolar degeneration, ending in loss of the nucleus. According to Lingelsheim (v. Lingelsheim), rabbit white blood cells are most sensitive to L., those of humans are much less sensitive, and frog white blood cells are completely insensitive. In a mixture of L. with white blood cells, methylene blue, as the white blood cells are destroyed, is restored, which allows one to visually judge the course of the reaction (Neisser and Wechsberg). Leucocidin is usually accompanied by hemotoxin, and both are found only in pathogenic staphylococci.