CD79a

Characteristics

The CD79 antigen is a heterodimer consisting of two phosphoproteins designated CD79a (mb-1; 47 kDa) and CD79b (B29; 37 kDa). CD79 associates to membrane-bound Ig to create the B-cell complex allowing signal transduction to be transmitted to the interior of the cell. CD79a is specific for B-cells (Fig 1), appearing before the pre-B cell stage, still being present at the plasma cell stage.

Neoplasms

CD79a is detected in the large majority of B-cell neoplasms (Fig 2). However, among plasma cell neoplasms, only about 50% are stained. CD79a has been reported in up to 10% cases of precursor T-cell lymphoblastic lymphoma but very rarely in mature T-cell lymphomas. In nodular lymphocyte predominant Hodgkin lymphoma, CD79a is found in of L&H cells in the large majority of cases, while in the other types, Reed-Sternberg cells are only stained in 20% of the cases. Among myeloid leukaemias, CD79a positivity has been described in type M3.

Application

Together with CD20, CD79a is one of the most important markers for the identification of B-cell neoplasms as outlined above.

Visualization

For formalin fixed, paraffin embedded material, mAb JCB117 is one of the most frequently used clones. For optimal epitope retrieval, HIER is needed, and an alkaline buffer is preferred. mAb HM57 cannot be recommended for paraffin sections because of cross reactivity with smooth muscle cells and various epithelia (see assessment, run 6). For control tissue, lymph node or tonsil is appropriate. B-cells in both the follicle centre and mantle zone as well as plasma cells should be stained.

Assessments

Run 6 2002

Run 21 2007

Run 29 2010

Selected references

Jaffe ES, Harris NL, Stein H, Vardiman JW (Eds.) WHO Classification of Tumours. Pathology and Genetics of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, IARC Press 2001.

Korkolopoulou P, Cordell J, Jones M, Kaklamanis L, Tsenga A, Gatter KC, Mason DY. The expression of the B-cell marker mb-1 (CD79a) in Hodgkin's disease. Histopathology. 1994 Jun;24(6):511-5.

Kurtin PJ, Hobday KS, Ziesmer S, Caron BL. Demonstration of distinct antigenic profiles of small B-cell lymphomas by
paraffin section immunohistochemistry. Am J Clin Pathol. 1999 Sep;112(3):319-29.

Mason DY, Cordell JL, Brown MH, Borst J, Jones M, Pulford K, Jaffe E,
Ralfkiaer E, Dallenbach F, Stein H, et al. CD79a: a novel marker for B-cell neoplasms in routinely processed tissue
samples. Blood. 1995 Aug 15;86(4):1453-9.

Pilozzi E, Pulford K, Jones M, Muller-Hermelink HK, Falini B, Ralfkiaer E, Pileri S, Pezzella F, De Wolf-Peeters C, Arber D, Stein H, Mason D, Gatter K. Co-expression of CD79a (JCB117) and CD3 by lymphoblastic lymphoma.
J Pathol. 1998 Oct;186(2):140-3.

Toth B, Wehrmann M, Kaiserling E, Horny HP. Immunophenotyping of acute lymphoblastic leukaemia in routinely processed bone marrow biopsy specimens. J Clin Pathol. 1999 Sep;52(9):688-92.

Vasef MA, Alsabeh R, Medeiros LJ, Weiss LM. Immunophenotype of Reed-Sternberg and Hodgkin's cells in sequential biopsy specimens of Hodgkin's disease: a paraffin-section immunohistochemical study using the heat-induced epitope retrieval method. Am J Clin Pathol. 1997 Jul;108(1):54-9.

Yao X, Teruya-Feldstein J, Raffeld M, Sorbara L, Jaffe ES. Peripheral T-cell lymphoma with aberrant expression of CD79a and CD20: a diagnostic pitfall. Mod Pathol. 2001 Feb;14(2):105-10.