Inducing specific reactivity against B cells in mice by immunizing with an Fc fusion protein containing self-Igβ

A recombinant chimeric fusion protein, muIgβ-huγ4.Fc, composed of the extracellular domain of mouse Igβ (CD79b) and the CH2-CH3 domains of human IgGγ4.Fc (huγ4.Fc), linked via an immunologically inert flexible peptide, was prepared. The fusion protein was evaluated for its ability to induce specific auto-reactive immune response against Igβ and to modulate B cell activity in Balb/c mice. Upon immunization with muIgβ-huγ4.Fc, mice developed immunoglobulin (IgG) against self-Igβ, which could bind to the cells of a mouse B cell line expressing Igβ on the cell surface. The proportion of B cells in mononuclear cells in the peripheral blood (PBMC) of treated mice decreased as compared to that of mice immunized with huγ4.Fc without the Igβ component. Furthermore, mice immunized against muIgβ-huγ4.Fc displayed a reduced antibody response against an irrelevant antigen. The implications of employing the present approach in developing a therapeutic strategy for regulating B cell activity has been discussed.