CD79a: a novel marker for B-cell neoplasms in routinely processed tissue samples.
Mason DY., Cordell JL., Brown MH., Borst J., Jones M., Pulford K., Jaffe E., Ralfkiaer E., Dallenbach F., Stein H.
The CD79 molecule, comprising two polypeptide chains, mb-1 (CD79a) and B29 (CD79b), is physically associated in the B-cell membrane with immunoglobulin. It transmits a signal after antigen binding and may, therefore, be considered the B cell equivalent of CD3. It appears before the pre-B-cell stage, and the mb-1 (CD79a) chain can still be present at the plasma cell stage. In this report, we describe a new anti-CD79a monoclonal antibody, JCB117, which reacts with human B cells in paraffin embedded tissue sections, including decalcified bone marrow trephines. When tested on a total of 454 paraffin embedded tissue biopsies, gathered from a number of different institutions, it reacted with the great majority (97%) of B-cell neoplasms, covering the full range of B-cell maturation, including 10 of 20 cases of myeloma/plasmacytoma. It is of interest that the antibody labels precursor B-cell acute lymphoblastic leukemia samples, making it the most reliable B-cell marker detectable in paraffin-embedded specimens in this disorder. All neoplasms of T cell or nonlymphoid origin were negative, indicating that antibody JCB117 may be of value to diagnostic histopathologists for the identification of B-cell neoplasms of all maturation stages.