Hemolysins

substances capable of liberating hemoglobin from red blood cells. Upon liberation by hemolysins, the hemoglobin dissolves in the plasma or surrounding fluid and the blood (or the suspension of red blood cells) becomes transparent (laked blood). Hemolysins are the products of the vital activities of many bacteria (for example, staphylococci and streptococci), parasitic worms, insects, scorpions, and some poisonous snakes (lysolecithins). Hemolysins may be present in the blood serum and lyse the body’s own red blood cells (autohemolysis). However, they generally appear after intravenous injection of red blood cells obtained from the same species of animal (isohemolysins) or from another species (heterolysins). The hemolytic properties of these serums, which depend upon the presence of complement (a thermolabile substance needed for the action of heterolysins upon red blood cells), are lost when they are heated to 56° C for 30 minutes.