Identification of a new serum protein polymorphism as transferrin.

By isoelectric focusing at pH 3.5--9.5, Kühnl and Spielmann (1977) recently demonstrated a new genetically determined serum protein polymorphism designated 'Hpa' because of an apparently specific reaction with antihaptoglobin. In this study the polymorphism was reproduced, but the components were found to focus at pH 5.8, which is different from the pI of haptoglobin, and immunologic relation to haptoglobin could not be confirmed. Using pure transferrin as a reference, the results of isoelectric focusing, crossed immunoelectrophoresis, and immunofixation indicated that the polymorphic components were identical to transferrin. This polymorphism does not correspond to the already known transferrin polymorphism, as the two usual genes, tentatively designated Tf1 and Tf2, in my population sample (n = 132) were 0.19 and 0.81, and, further, all individuals except three in the sample belong to type Tf-C.