Studies of monkey complement: Measurement of cynomolgus monkey CH50, ACH50, C4, C2 and C3

Background: The cynomolgus monkey is commonly used as the recipient in transplantation experiments. However, study of the complement system of cynomolgus monkeys is lacking. In the present study, the complement system of cynomolgus monkeys was compared with that of humans, by checking hemolytic titers. Methods: Hemolytic titers of complement from cynomolgus monkeys were calculated using the same methods as are used in humans. The complement regulatory function of human decay accelerating factor (DAF, CD55) in cynomolgus monkey serum was next studied using erythrocytes from human DAF-transgenic pigs. Results: The results indicated relatively high values, except for C4: CH50: 211.19 +/- 42.78 units/ml, ACH50: 51.47 +/- 12.43 units/ml, C4: 30 170 +/- 14 300 SFU/ml C2: 33831 +/- 7442 SFU/ml and C3: 93612 +/- 30131 SFU/ml. Western blot experiments using antibodies for human complement components revealed similarities between the cynomolgus monkey and human complement systems. Human DAF inhibited pig erythrocyte lysis from approximately 60-70% to 17% in both human and cynomolgus monkey sera, indicating an almost identical complement regulatory function. Conclusion: The hemolytic titer of cynomolgus monkeys was greater than the titer measured in human serum. However, human DAF showed nearly the same complement regulatory function in both human and cynomolgus monkey sera.