Transferrin: evidence for two common subtypes of the TfC allele

Evidence is presented for an extended polymorphism of human transferrin (Tf). Three common phenotypes were observed among TfC individuals after isoelectric focusing of sera on polyacrylamide gels. They are explained in terms of two subtypes of the TfC allele, tentatively designated TfC1 and TfC2. The distribution of the phenotypes Tf C1, C2-1, and C2 provides a good fit to the Hardy-Weinberg equation. In our population sample (n = 942) the following frequencies were calculated: TfC1 = 0.8195, TfC2 = 0.1720, TfB2 = 0.0064, TfB1-2 = 0.0016, and TfD1 = 0.0005. Family studies (n = 112) indicate an autosomal codominant way of inheritance. The observed subheterogeneity is detectable in purified transferrin after isofocusing and subsequent immunofixation. The subtypes are still present after treatment of sera with neuraminidase.