Monoclonal antibodies to cyclosporin are representative of the major antibody populations present in antisera of immunized mice.

Two series of mouse antisera raised against cyclosporin (Cs)-carrier conjugates exposing opposite sides of the Cs molecule and more than sixty monoclonal antibodies (mAbs) derived from the same animals were compared in terms of isotype and fine specificity for Cs. The predominant isotypes of the mAbs reflected the in situ distribution of the circulating anti Cs antibodies. The fine specificity of the antibodies was studied by determining their cross-reactivity for a series of Cs-derivatives and Cs-metabolites in competitive ELISA. The antisera raised by different immunizations showed very different cross-reactivity patterns for the Cs-derivatives. However, the in situ anti Cs antibody populations and the majority of mAbs derived from the corresponding animals showed a striking similarity in fine specificity for restricted clusters of residues on the Cs molecule. These results indicate that the mAbs produced against Cs are representative of the major antibody population present in the sera of the mice used for the fusion. By determining the characteristics of antibodies found in the serum of immunized mice it may thus be possible to select animals that are likely to give rise to mAbs of a certain isotype and specificity.