Stains & CD markers
CD79a


Last author update: 13 February 2024
Last staff update: 13 February 2024

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PubMed Search: CD79a

See Also: CD79b

Narendra Bhattarai, M.D.
Genevieve M. Crane, M.D., Ph.D.
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Cite this page: Bhattarai N, Malhotra S, Crane GM. CD79a. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cdmarkerscd79a.html. Accessed May 19th, 2024.
Definition / general
  • CD79a, identified as the alpha chain of the B cell antigen receptor complex, is a transmembrane protein synthesized by the CD79A gene located on chromosome 19
  • Expressed over full range of B cell development from early B cell precursors, preceding immunoglobulin heavy chain gene rearrangement and persisting through B cell maturation (Blood 1995;86:1453, Appl Immunohistochem Mol Morphol 2001;9:97)
Essential features
  • CD79a / CD79b are membrane bound immunoglobulins that form the B cell receptor (BCR) complex
  • Expressed from early B cell precursors until advanced plasma cell stages (Blood 1995;86:1453)
  • Membranous and cytoplasmic expression useful for confirming B cell lineage or following therapy with monoclonal antibodies against other B cell antigens
Terminology
  • Also called MB1 membrane glycoprotein, IgMα and Igα
Pathophysiology
  • CD79a, a 226 amino acid membrane protein, is the product of the human mb1 gene situated on chromosome 19, specifically at band q13.2 (OMIM: CD79A Antigen; CD79A [Accessed 23 January 2024])
  • Has single extracellular immunoglobulin domain, a transmembrane domain and an intracytoplasmic signaling domain with an immunoreceptor tyrosine based activation motif (ITAM)
  • Heterodimerizes with CD79b (B29) and constitutes an integral component of the B cell receptor (BCR) complex
  • CD79a's cytoplasmic domain enables signal transduction via antigen binding to the BCR, causing rapid protein tyrosine phosphorylation and activation of pathways through the immunoreceptor tyrosine based activation motif (ITAM) (Front Immunol 2018;9:665)
  • CD79a and CD79b are required for surface IgM expression in human B cells (J Immunol 2022;209:2042)
Clinical features
  • Deletions or mutations in the genes encoding CD79a lead to developmental arrest at the pre-B cell stage and can be a cause of agammaglobulinemia (J Clin Invest 1999;104:1115)
  • Plays an important functional role in maintaining the immature, immune suppressive phenotype of myeloid derived suppressor cells (MDSC) and in inducing the secretion of protumorigenic cytokines, thus, may be a novel target for cancer therapy (PLoS One 2013;8:e76115)
  • Impairment of the glycosylation of μ and CD79a chains is associated with lower levels of expression of IgM in chronic lymphocytic leukemia (Blood 2005;105:2933)
  • Synovial infiltration of CD79a positive B cells correlates with joint destruction in rheumatoid arthritis (J Rheumatol 2011;38:2301)
  • Aberrant staining in megakaryocytes in postinduction acute lymphoblastic leukemia (ALL) cases (cytoplasmic and granular) (Hum Pathol Case Rep 2021;23:200467)
  • Aberrant CD79a positivity in erythroid precursors postchemotherapy in lymphoma patients can complicate minimal residual disease detection after rituximab treatment (Haematologica 2007;92:855)
Interpretation
  • Membranous and cytoplasmic expression is considered positive; pro-B cells may only show cytoplasmic expression (J Immunol 1991;147:2474)
Uses by pathologists
Prognostic factors
  • Some studies report that cytoplasmic CD79a expression is associated with lower survival odds than classical acute myeloid leukemia (AML) with t(8;21)(q22;q22) (Korean J Lab Med 2007;27:388)
  • Cytoplasmic CD79a can be used in monitoring of relapse in B ALL post-CD19 chimeric antigen receptor (CAR) T cell therapy (Leuk Lymphoma 2022;63:426)
  • CD79a may have independent prognostic relevance for CNS involvement and CNS relapse in pediatric B cell precursor ALL (Commun Biol 2021;4:73)
  • CD79a positivity may be associated with worse prognosis in classic Hodgkin lymphoma compared to CD79a negative classic Hodgkin lymphoma (J Clin Exp Hematop 2020;60:78)
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Narendra Bhattarai, M.D. and Shikha Malhotra, M.D.
CD79a stain in reactive follicles

CD79a stain in reactive follicles

Marginal zone lymphoma

Marginal zone lymphoma

CD79a stain, marginal zone lymphoma

CD79a stain, marginal zone lymphoma

Diffuse large B cell lymphoma

Diffuse large B cell lymphoma

CD79a stain, diffuse large B cell lymphoma

CD79a stain, diffuse large B cell lymphoma

CD79a stain, NLPHL

CD79a stain, NLPHL

Positive staining - normal
Positive staining - disease
Negative staining
Sample pathology report
  • Cervical lymph node, excisional biopsy:
    • Nodular lymphocyte predominant Hodgkin (B cell) lymphoma (see comment)
    • Comment: Histologic sections show lymphoid infiltrate in diffuse and vaguely nodular patterns. The lymphoma cells are large with scant to moderate cytoplasm and large nuclei with fine chromatin (LP cells). These cells are in a background of numerous small, mature lymphocytes and epithelioid histiocytes. Immunohistochemical stains show the large, abnormal cells are positive for CD20, CD45, CD79a, BCL6 and PAX5. They are negative for CD3, CD4, CD5, CD8, CD10, CD15, CD30, ALK1, BCL2 and fascin. The large, abnormal cells overlap networks of CD21 positive follicular dendritic cells. Chromogenic in situ hybridization studies with probes for Epstein-Barr virus (EBV) encoded small RNA (EBER) are negative. PD-1 is positive on small, mature T cells surrounding the LP cells.
Additional references
Board review style question #1

In Hodgkin lymphoma, what is the usual pattern of CD79a expression in Hodgkin and Reed-Sternberg (HRS) cells?

  1. Complete absence of expression
  2. Diffuse and strong positivity
  3. Focal and variable expression
  4. Staining restricted to the nodular areas
Board review style answer #1
A. Complete absence of expression. Despite originating from B cells, Hodgkin and Reed-Sternberg (HRS) cells in classic Hodgkin lymphoma exhibit a disrupted B cell program, resulting in the loss or downregulation of numerous B cell markers. These include pan-B cell antigens, such as CD19, CD20, CD22 and CD79a, as well as B cell transcription factors, such as OCT2, BOB.1 and BCL6. Answers B and D are incorrect because they do not represent the usual pattern of expression in Hodgkin lymphoma. Answer C is incorrect because some cases may show weak expression of CD79a but it is not the typical pattern.

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Reference: CD79a
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