Quantitation of immunoglobulin classes and subclasses in anti-Rh (D) antibodies.

The isotype profiles of anti-Rh (D) antibodies were measured from 16 serum samples with a solid-phase radioimmunoassay that employed monoclonal anti-isotype antibodies. These antibodies had been standardized in another solid-phase system with the aid of monoisotypic antibodies (e.g., anti-tetanus toxoid of isotype IgG4), and this permitted calculations of the relative concentrations of different isotypes in each anti-D population. Of the heavy-chain isotypes, only IgG1 and IgG3 were found in anti-Rh (D) antibodies. The share of IgG1 varied from 100% (2 sera) to 0% (1 serum) of detected units, and the mean proportion was 73.8%. The remainder was IgG3 (mean share 26.2%). The proportions of kappa and lambda immunoglobulins varied greatly in individual sera, in three sera only kappa Ig and in one serum only lambda Ig could be detected.