A monoclonal anti-C4d that demonstrates a specificity related to anti-Ch

A monoclonal anti-C4d reagent, L003, agglutinated untreated and trypsin-treated C4A Rodgers(Rg)- and C4B Chido(Ch)-coated red cells. Inhibition of the agglutination, regardless of the Rg/Ch phenotype of the C4 coat, showed Ch specificity, more precisely, for the Ch1 determinant. C4A allotypes that express Ch1 and Ch3 rather than Rg1 and Rg2, and C4B allotypes that express Rg1 rather than Ch1, Ch2, or Ch3 confirmed that the inhibition specificity in serologic tests was anti-Ch1 and not anti-C4B.