A high incidence of C9 deficiency among healthy blood donors in Osaka, Japan

By the use of sucrose gelatin veronal buffer (SGVB), a simple screening test was developed by us to detect sera with low complement activity, including C9-deficient sera. Using this screening test, we were able to identify sera with low complement activity including C9-deficient sera among a large number of samples. Further examinations, estimation of the protein concentration of C9, C4, C3, etc., enabled classification of serum with low complement activity into C9-deficient serum, serum deficient In the other components, and serum with low complement activity caused by non-specific activation of complement through the classical pathway by low temperature In vitro. Among 145,640 sera from Osaka donors, 138 sera were found to be deficient in C9 by these methods. The whole complement activity (CH50) of the 138 sera was 13.1 +/- 3.0 U/ml. The C9 protein in these sera was undetectable, not only by the single radial immunodiffusion method, but also by the sensitive ELISA method. C9 activities In these sera were less than 0.1% of the level in pooled normal human serum. These findings and the family studies revealed that 138 blood donors unquestionably had a hereditary C9 deficiency. The incidence of C9 deficiency among Osaka donors was calculated to be 0.095%.