A simple method for separation of uninfected erythrocytes from those infected with Plasmodium berghei and for isolation of artificially released parasites.

Rat erythrocytes infected with Plasmodium berghei were disrupted by gentle passage of Concanavalin A (Con A) agglutinated cells through a 100 mesh stainless steel grid. The free parasites were separated from cell debris, unbroken infected cells, and from uninfected rat erythrocytes on a Percoll gradient. The parasites remained morphologically intact, metabolically active, and infective to mice. The parasites were observed by light and electron microscopy. The incorporation of 3H-isoleucine and 3H-hypoxanthine was compared in intact and infected cells, and the infectivity was measured by the injection of parasites into susceptible mice. It seems that the combination of the two techniques used, produces a high yield of intact free parasites suitable for physiological or immunological studies.