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

Abstract

A study was made of polyspecific human allo-anti-C4, anti-Chido (Cb), which reacts with determinants usually located on C4B protein. Some anti-Cb reagents are capable of reacting with Cb- red cells coated with C4 from Cb:−1,−2,−3 donors. A complex serologic pattern demonstrated three more Cb determinants, Cb4, Cb5, and Cb6, which were detected by bacmagglutination-inhibition tests. All Cb:1,2,3 samples were Cb:4,5,6 but samples lacking one or more of the Cb1,Cb2,Cb3 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. Cb4 always associates with C4B protein. Cb5 and Cb6, 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.