An international reference typing for Ch and Rg determinants on rare human C4 allotypes.

Red cells, serum and plasma samples of 20 individuals, selected for their C4 allotypes, were distributed from Bonn to five laboratories, for investigation of their Chido (Ch) and Rodgers (Rg) determinants. One anti-Ch (M.H.) and one anti-Rg(Prest.) were distributed, but the individual laboratories also used their own reagents and their own typing methods. There was general agreement in interpretation of the majority of samples. Partial inhibition for Ch and Rg was detected. Two samples gave anomalous results; one sample with C4 A1,3 BQO, QO had Ch determinants on the red cells and in plasma (partial inhibition), and another sample with C4 A3,4 B5, QO apparently lacked Ch determinants on the red cells and in plasma. Heterogeneity of anti-Ch and anti-Rg was suggested in testing red cells, perhaps, reflecting a quantitative effect. This heterogeneity was confirmed by inhibition studies. The capacity of some reagents to detect partial inhibition probably reflects qualitative as well as quantitative differences.