Development of a hemolytic assay for mouse complement components in sera and the variation of their levels with age.

The hemolytic activity of C1, C4, C2 and C3-9 of mouse complement in serum could be measured by using each intermediate cells with guinea pig or human complement components. C3 was assayed by immune adherence. Sheep erythrocytes (SRBC) sensitized with rabbit IgM antibody produced no or feeble lysis in the assay for C4 and C2, whereas SRBC sensitized with IgG antibody or unfractionated antiserum did significant lysis. Using these assays, the activity of each component in sera of several H-2 congenic strains was examined. The age-dependent changes of each component levels in BALB/c mice of both sexes were also examined. The differences in levels of C4 and C2 in sera from several strains were not significant in both sexes, while the levels of C3-9 were higher in males than in females. The levels of each component increased with age. The levels of C4 activity and the Ss protein showed good correlation in males but not in females. The correlation between the levels of C3-9 activity and the MuB1 protein was detected in both sexes.