Erythrocytes from CD59^−/− mice are susceptible to C lysis.

Four lytic assays were used to test lytic susceptibility of CD59^−/− erythrocytes. In each case, erythrocytes from 3 mice of each group were tested and results are means (± SDs) of the percentage of lysis for the 3. (A) Classical pathway assay. Erythrocytes were sensitized and exposed to dilutions of rat (closed symbols) or mouse (open symbols) serum. CD59^+/+ (diamond) and CD59^+/− (square) erythrocytes were lysed significantly only at the highest serum doses used (1:10), whereas CD59^−/− (triangles) erythrocytes were almost completely lysed at this dose when exposed to rat serum, 80% lysed at the same dose of mouse serum and were measurably lysed at all serum doses tested. (B) CVF-triggered reactive lysis assay. Unsensitized erythrocytes were incubated with CVF and dilutions of rat (closed symbols) or mouse (open symbols) serum. CD59^+/+ (diamond) and CD59^+/− (square) erythrocytes were not lysed even at the highest serum doses used (1:10), whereas CD59^−/−(triangles) erythrocytes were almost completely lysed at this dose of either rat or mouse serum and were measurably lysed at all doses tested. (C) C5b-7 site assay. Erythrocytes bearing preformed C5b-7 sites were incubated with dilutions of rat (closed symbols) or mouse (open symbols) serum in PBS as source of C8/C9. Even at the highest dose (1:40), neither rat nor mouse serum lysed CD59^+/+(diamond) and CD59^+/− (square) erythrocytes, whereas CD59^/ (triangle) erythrocytes were 80% lysed when exposed to rat serum and 50% lysed by mouse serum at this dose and were measurably lysed at all serum doses. (D) A modified Ham test in which unsensitized erythrocytes were incubated at 37°C with acidified serum. CD59^−/− erythrocytes were lysed more than 40%, whereas CD59^+/+ and CD59^+/− erythrocytes were not significantly lysed.