Monoclonal Antibodies to Immunoglobulin Allotypes: Specificity and Reactivity in Haemagglutination and ELISA Techniques

Summary

Monoclonal antibodies (McAbs) were prepared to further study the allotypes of immunoglobulins. By screening supernatants in the haemagglutination-inhibition (HAI) as well as in the ELISA techniques anti-G1m(z) (=5A1) and anti-G1m(a) (=1C2) antibodies could be obtained.

These two antibodies are specific for the corresponding allotypes in inhibition assays performed with the HAI and the ELISA, but only under special circumstances. When McAb 5A1 is used in the direct haemagglutination test (HA) there is some cross-reactivity with other IgG coated cells.

This reaction is not inhibitable. However in the HAI with Glm(z) coated cells and in the indirect ELISA with G1m(z) coated plates only G1m(z) positive samples inhibit. McAb 1C2 shows another picture, because it reacts in the direct HA as well as in the direct ELISA with IgG of all subclasses and allotypes. In inhibition tests with G1m(a) coated cells only G1m(a) positive samples inhibit; with other IgG coated cells IgG of all subclasses and allotypes inhibit. It could be shown that the epitope, detected by 5A1 is located in the CH1 domain and the epitope(s) detected by 1C2 is/are located in the CH3 domain.

In conclusion, McAbs 5A1 and 1C2 are both useful anti-Gm reagents. However McAb 1C2 seems to have a dual specificity, namely anti-Gm(a) and anti-IgG. The question is, is the G1m(a) specificity a pseudospecificity, in other words are we deal ing here with an anti-IgG antibody with a prevalence for G1m(a) positive molecules.