IgG subclass levels and southern analysis of DNA in primary immunodeficiency diseases including IgG subclass deficiency

Serum IgG subclass levels are reported for twenty patients with primary immunodeficiency diseases, including four patients with IgG subclass deficiency, using an enzyme-linked immunosorbent assay with monoclonal antibodies. The disorder of each patient with IgG subclass deficiency seemed to be heterogeneous immunologically and clinically. One had complete IgG2-IgG4 deficiency, another had IgG2-IgG4-IgA deficiency and the other two had IgG2-IgA deficiencies. We did not find any structural-gene deletions in the constant region of the human immunoglobulin heavy-chain locus. Although the possibility of defects in genes controlling immunoglobulin expression, or small mutations, remains, these results suggest that IgG subclass deficiency is not always linked to particular structural-gene deletions.