Rat monoclonal antibodies to mouse IgG1, IgG2a, IgG2b, and IgG3 subclasses, and kappa chain isotypic determinants.

Rats of the LOU/Ws1 strain were immunized with mixtures of mouse monoclonal antibodies (MAbs) of various isotypes, and their spleen cells were fused with the rat myeloma Y3.Ag1.2.3 or the mouse myeloma X63.Ag8.653. From four fusion experiments, we have selected 14 rat MAbs that exhibited selective binding to either IgG2a, IgG2b, IgG1, and IgG3 subclasses or to kappa chain isotypic determinants. Cross-blocking studies revealed that three rat MAbs identified distinct determinants on the Fc fragment of the MAb H10-81.10 (A.TH, Igh-1e). By contrast, the IgG1, IgG2b, IgG3, and kappa isotypes defined by the mAbs analyzed in this study were found to be in close spatial relationship. These rat MAbs bound IgG2a, IgG2b, or IgG1 mouse MAbs, expressing the Igh-1e,j,a, or c, Igh-3a or b, or Igh-4a or b allelic specificities, respectively.