Gm allotypes in IgA deficiency.

Gm phenotypes were examined in 90 Swedish IgA-deficient (less than 0.05 g/litre of serum IgA) donors and 40 normal first and second degree relatives of six of these donors. The G1m1,2, G3m5 and Km1 frequency in the group of IgA-deficient donors did not differ from that found in the normal population. Among the relatives, HLA and/or Gm identical normal sibs were observed. Anti-IgA antibodies were present in 29 of the IgA-deficient donors and anti-IgG in seven. No association between the two was found. A statistically significant association between the G1m-2 phenotype and the presence of anti-IgA antibodies was observed. When subdivided according to HLA type, a non-random distribution of Gm phenotypes was seen in HLA-B8/DR3 positive individuals with anti-IgA antibodies (HLA-B8/DR3 being the haplotype associated with IgA deficiency). These data suggest an association between IgA deficiency, anti-IgA and the studied Gm allotypes.