C4 allotypes and HLA-DR antigens in the family of a patient with C4 deficiency

Glomerulonephritis associated with complete deficiency of the fourth component of complement. Response to intravenous immunoglobulin

A 15-year-old girl with complete C4 deficiency and a lupus-like disorder developed evidence of nephritis after 4 years of followup. Renal biopsy demonstrated an immune complex glomerulonephritis, with deposits in the capillary loops, the paramesangium, and the mesangial matrix. Renal function was normal. The patient was treated with monthly infusions of intravenous immunoglobulin for 6 months. The treatment was well tolerated, and resulted in resolution of the rash and hematuria. Followup biopsy showed less proliferation and fewer loop deposits. In light of the serious risk of infections that is associated with complement deficiency, approaches to glomerulonephritis that do not include immunosuppression should be considered.

Three Chido determinants detected on the B5Rg+ allotype of human C4: their expression in Ch-typed donors and families

A study was made of polyspecific human allo-anti-C4, anti-Chido (Ch), which reacts with determinants usually located on C4B protein. Some anti-Ch reagents are capable of reacting with Ch- red cells coated with C4 from Ch:-1,-2,-3 donors. A complex serologic pattern demonstrated three more Ch determinants, Ch4, Ch5, and Ch6, which were detected by haemagglutination-inhibition tests. All Ch:1,2,3 samples were Ch:4,5,6 but samples lacking one or more of the Ch1,Ch2,Ch3 series of determinants also lacked some of the new determinants. MHC typed families demonstrated the inheritance of the new determinants as part of the Ch haplotype, and associations with C4 allotypes and haplotypes have been established. Ch4 always associates with C4B protein. Ch5 and Ch6, normally detected on C4B protein, were detected in several individuals who lacked C4B (BQO allotypes) and were therefore presumed in these instances to be located on the accompanying C4A protein.