Application of immunoglobulin heavy chain (GM, AM) and light chain (KM) allotypes to cases of disputed paternity.

To evaluate the usefulness of extended immunoglobulin allotyping compared to the conventional number of reagents in general use, 1,896 cases of disputed paternity tested for HLA, immunoglobulin allotypes (IGH, [GM, AM] and KM) and red blood cell markers (RBC) (ABO, RH, MNS, Kidd, Duffy, Kell, Colton, Lutheran, and Lewis) were analyzed. There were 1,289 cases in which both the mother and alleged father were Black, 548 cases in which the mother and alleged father were White and 59 cases that were either mixed or of different ethnic groups. A total of 691 exclusions were observed (533 Black, 143 White and 15 other). The observed exclusion rates for the HLA system in Blacks (93.9%) and in Whites (94.9%) were similar to previous estimates of the HLA exclusion rates, indicating that these cases appear to be consistent with other studies. The observed exclusion rates for the IGH haplotypes (alleles) were the highest single system exclusion rates beside the HLA system (54.08% in Blacks and 31.47% in Whites). Further, the values were higher than any single blood group system, or electrophoretic system in common usage. The combined IGH and KM observed exclusion rates were 57.50% for Black cases and 37.06% for White cases. The value of the combined immunoglobulin allotypes in Blacks almost exceeds the combined exclusion rate for all RBC antigens tested. The importance of doing extended immunoglobulin allotyping in Black cases is demonstrated by the fact that 76.5% of the exclusions would have been missed if only G1M A, F and X and G3M B0 and G had been used in the Black cases. The inclusion of additional markers in the White cases increased the observed IGH exclusion rate from 23.78 to 31.47%. The increase was primarily due to the addition of G2M N.