The present invention is directed to bi-specific monovalent diabodies that comprise an immunoglobulin Fc Domain ("bi-specific monovalent Fc diabodies") and are composed of three polypeptide chains and which possess at least one binding site specific for an epitope of CD32B and one binding site specific for an epitope of CD79b (i.e., a "CD32B x CD79b bi-specific monovalent Fc diabody"). The bi-specific monovalent Fc diabodies of the present invention are capable of simultaneous binding to CD32B and CD79b. The invention is directed to such compositions, to pharmaceutical compositions that contain such bi-specific monovalent Fc diabodies and to methods for their use in the treatment of inflammatory diseases or conditions, and in particular, systemic lupus erythematosus (SLE) and graft vs. host disease.
