The distribution of immunoglobin allotypes in two Tlaxcaltecan populations.

The distribution of Glm(f, z, a, and x), G3m(b0, b1, b3, b5, c3, c5, g, s, t and v), A2m(1 and 2) and Km(1) (formerly Inv(1)) allotypic determinants has been examined in specimens from the inhabitants of two transplanted Tlaxcaltecan villages (Cuanalan and Saltillo). The results indicate that Gmza;g Am1, Gmza;g Am2, Gmzax;g Am1, Gmza;bst Am1, Gmza;bst Am2, Gmf;b Am1, Gmza,b Am1, Gmza;b Am2 and Km1 are polymorphic or marginally polymorphic in both populations, while Gmza;bc3,5 Am2, Gmza;bs Am2, and Gmzax;g Am2 were detected only in Saltillo. Two related individuals from Saltillo have either a Gmf;g Am1 or Gmf;-Am1 haplotype while a third unrelated individual had either a Gmf;g Am1 or Gm-;g Am1 haplotype. The frequencies observed for "residents" of Cuanalan are similar to those for other Indian populations in Mexico. Estimation of Caucasian and African admixture within the two communities indicates significant heterogeneity among the inhabitants of Cuanalan, in that Tlaxcaltecan residents have no detectable African admixture and significantly less Caucasian admixture than recent immigrants, with Tlaxcaltecan-immigrant hybrids intermediate, while no significant variation was observed among the subdivisions of Saltillo. However, Saltillo has greater Caucasian and African admixture than Cuanalan. Admixture estimates based on Gm haplotypes appear to agree much better with known historical events than those generated by blood groups, indicating that Gm is a better estimator of admixture than blood groups under certain circumstances.