The distribution of the third complement component and other polymorphic traits in rheumatoid arthritis.

The distribution of C'3 phenotypes in 61 seropositive rheumatoid arthritis patients and 464 normal blood donors in Tokyo was examined by high-voltage agarose gel electrophoresis. The allele of the common European variant, C3(F), is absent in Japanese, but another F allels, C3(Frare), is present with a frequency of 0.025 and 0.013 in RA patients and blood donors, respectively; the difference is not statistically significant. The distribution of phenotypes for several other enzyme systems was also determined in an attempt to detect association with RA Again, no statistically significant differences were found.