Restriction in the lytic efficiency of complement of different erythrocyte targets: a re-examination of the activities of horse C8 and C9.

Differences in the lytic efficiency of different complement sources have frequently been observed. This effect has been shown to be related to both the species of the target erythrocyte and the species composition of terminal complement components within the 5b-9 membrane attack complex. The majority of studies have indicated that the source of C9 is critical in controlling the range of erythrocyte species that can be lysed efficiently. One exception to this general finding was the report by Lachmann et al., 1973 (Immunology 24, 135-145), using horse serum as a complement source. In that study, horse C8 rather than C9 was implicated as the critical component. In this study, we have re-examined this observation and find that the restricted hemolytic potential of horse complement correlates absolutely with the presence of horse C9. The reason for the differences between our findings and those of the earlier study are discussed.