Partial γ1 fragment is a ‘natural’ bovine IgG1 fragment without detectable class-specific γ determinants

Abstract

IGG in bovine sera generally consists of a mixture of the two subclasses IgG1 and IgG2. While testing the reliability of the radial immunodiffusion (RID) method for quantifying IgG in bovine body fluids¹, we found a discrepancy. With most sera tested, the combined amounts of IgG1 and IgG2 determined using subclass-specific antisera was equal to the amount of IgG determined with class-specific antisera against γ determinants, that is common to IgG1 and IgG2. But with a few sera the amounts were not equal (unpublished results). (Class-specific antisera against γ determinants were produced by removing antibodies against subclass determinants on immunoadsorbent columns, starting from antisera which contained antibodies against both class (=γ) and subclass (=γ1 and/or γ2) determinants.) Using immunoelectrophoretic (IE) analysis, we have now shown that those sera contain a ‘fast’ IgG component as well as both IgG subclasses. The third component was represented by an arc in the anodic region of the precipitation pattern, and it proved partially identical to that of IgG1 (Fig. 1). Such an arc can be seen in a photograph of IE patterns of sera from calves infected with Trypanosoma vivax, although the arc is not mentioned in the report².