Variability in the susceptibility of erythrocytes prepared from 19 sheep. A405 of the culture supernatants and counts of parasitemia were measured 49 and 66 h after culture inoculation with B. divergens clone 2802C D5 (2.106 iRBC/mL) in 2 mL-well (RPMI 1640, sheep serum at 10%, 1.109 RBC/mL) for each sheep. Each A405 data point represents the average value of the triplicate culture pellets, and the error bars indicate the standard deviation. Parasitemia was calculated from the RBC obtained by mixing the triplicate culture pellets. In the insert, the regression analysis performed on the data from each method at 66 h post-inoculation is shown, as well as the regression coefficient. This experiment was also performed with the clone Rouen F5 with similar results (see Tab. I; Exp. 3).