10/6/03 Immunoglobulin deficiencies and susceptibility to infection in C2 deficient individualsSummaryThere is an increased susceptibility to bacterial infections in about 25% of individuals with congenital homozygous C2 deficiency. Alper et al of the Harvard Medical School in Boston, MA have investigated serum immunoglobulin and other protein levels in individuals with C2 homozygote deficiency. They found IgG4 deficiency in 85% of C2 deficient with recurrent infections and in 64% of C2 deficient without such infection. IgD deficiency was equally common in C2 deficient with and without recurrent infections. Serum IgA levels were also significantly lower in those with than without infections. In contrast, serum levels of IgG1, IgG3 and IgM were either similar to or higher in C2-deficient than in normal controls. The authors concluded that homozygous C2 deficiency is frequently associated with serum Ig abnormalities, some of which (in IgG4 and IgA levels) may contribute to increased susceptibility to infection. Reference J Clin Immunol 2003; 23:297-305 Editor’s Comments Traditionally, individuals with congenital C2 deficiency have been thought to be prone to developing lupus and other connective tissue inflammatory diseases but not an increased susceptibility to infection. However, more recently, there has been evidence that there is an increased frequency of infections in some homozygous C2 deficient individuals. The report described above raises the possibility that IgG4 and IgA deficiency may play role in such C2-deficient individuals (although the majority of individuals with isolated IgA deficiency do not have recurrent infections). Before drawing any conclusions I think that we must first see the patterns of protective antibody responses to pathogenic bacteria in these C2-deficient individuals following immunization with bacterial protein and polysaccharide antigens.
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