In vivo activation of quiescent B cells by anti-immunoglobulin. II. Production of lysozyme-specific monoclonal antibodies of desired isotype.

We wished to determine whether injection of mice with anti-isotype antibody would be a means to regulate in vivo isotype expression and to obtain hybridomas secreting monoclonal antibodies (mAbs) of desired antigen specificity and isotype. Treatment with a rat mAb (7D2) reactive with both the IgG2a and IgG2b isotypes of mouse Ig resulted in large increases in the serum concentrations of mouse IgG2(a + b). Moreover, injection of antigen-7D2 conjugates had a profound effect on the isotype distribution of hybridomas subsequently obtained from these animals. Thus, while greater than 95% of anti-hen eggwhite lysozyme (HEL) mAbs prepared from mice immunized with HEL alone were of the IgG1 isotype, 12/15 (80%) of the mAbs from mice injected with HEL-7D2 conjugates were of the IgG2a or IgG2b isotype. When tested for effector functions using HEL-coated erythrocytes, the mAbs showed the expected activities, i.e., the IgG2, but not IgG1 anti-HEL mAbs were able to fix complement, bind protein A, and mediate antibody-dependent cytotoxicity and phagocytosis. These results indicate that in vivo immunization with anti-isotype-antigen conjugates can be used to produce hybridomas of predetermined antigen and isotype specificities.