Cd 79A Immunohistochemistry Biopsy Tissue

CD79a stains the cytoplasm and membrane of B lymphocytes and megakaryocytes. CD79a is a protein expressed on the surface of B lymphocytes at all stages of maturation, from B-lymphocyte precursors through plasma cells. Its function is to transduce the signal of antigen binding to immunoglobulin into the cytoplasm of the B lymphocyte initiating intracellular signaling. Antibodies to CD79a are diagnostically useful to demonstrate B cell lineage of acute lymphoblastic leukemia, malignant lymphomas and chronic lymphoproliferative disorders. CD79 is composed of CD79a and CD79b components expressed almost exclusively on B cells and B-cell neoplasms. CD79a and CD79b expression precedes immunoglobulin (Ig) heavy-chain gene rearrangement and CD20 expression during B-cell ontogeny and disappears later than CD20 in the late (plasma cell) stage of B-cell differentiation. Therefore, antibodies to CD79a and CD79b are useful in the differential diagnosis of B-cell neoplasms from T-cell neoplasms or myeloid neoplasms, or L and H lymphocyte predominance Hodgkin's lymphoma from classic Hodgkin's lymphoma. In addition, CD79a and CD79b antibodies are useful markers in the diagnosis of precursor B-acute lymphoblastic leukemia (pre-B-ALL) because many of these tumors are negative for other B-cell markers, such as CD20 and CD45RA. Furthermore, for B-cell neoplasms, wherein CD20 expression is aberrantly lost, such as in diffuse large B-cell lymphoma, or for B-cell neoplasms after CD20-antibody therapy, CD79a may be used as a first-line B-cell marker for the diagnosis.