Expression of immunoglobulin lambda chains in the laboratory rat.

We immunized a BALB/c mouse with the lambda-bearing rat IgG1 myeloma IR31, fused its spleen cells with the hybridoma parent line P3.X63.Ag8.653, and isolated a monoclonal antibody (G33/11) directed against rat immunoglobulin lambda chains. We used this antibody to classify two existing rat hybridomas as lambda-bearing proteins (D4.37HL.252 and PC61.5), and isolated one new lambda-bearing rat IgM hybridoma, G36/1. All the normal inbred rat sera that were tested contained lambda-bearing Ig as detected by G33/11, at levels ranging from 1.5% to 13% of the total serum Ig, the mean value being 7.9%. This antibody will be valuable for broadening our understanding of the immunogenetics of the rat, and for the characterization of monoclonal antibodies made in this species.