CD79B molecule | Elisa - Clia - Antibody - Protein

Background

CD79B, also known as Ig-beta, is a protein encoded by the CD79B gene in humans. It is an integral component of the B cell receptor (BCR) complex, which is crucial for B cell development, activation, and function. The BCR complex consists of membrane-bound immunoglobulin (Ig) molecules associated with the CD79A (Ig-alpha) and CD79B (Ig-beta) heterodimer. This complex plays a pivotal role in the immune system by recognizing specific antigens, initiating signaling cascades that lead to B cell activation, proliferation, and differentiation. The importance of CD79B in immune responses and its implications in various clinical conditions make it a significant focus of immunological research.

Protein Structure

CD79B is a transmembrane protein comprising 229 amino acids. Its structure includes several distinct regions that contribute to its function within the BCR complex:

• Extracellular Domain: The N-terminal extracellular domain of CD79B contains an immunoglobulin-like domain. This domain is crucial for the interaction with the surface immunoglobulin molecules and the formation of the BCR complex. The extracellular domain also contains glycosylation sites that are important for protein stability and function.
• Transmembrane Domain: The transmembrane region of CD79B anchors the protein in the B cell membrane and allows it to interact with CD79A (Ig-alpha) to form a stable heterodimeric complex. This interaction is essential for the proper assembly and surface expression of the BCR complex.
• Intracellular Domain: The intracellular C-terminal region of CD79B contains immunoreceptor tyrosine-based activation motifs (ITAMs). These ITAMs are phosphorylated by Src-family kinases upon antigen binding to the BCR, initiating intracellular signaling cascades that lead to B cell activation and other downstream effects.

Classification and Subtypes

CD79B belongs to the immunoglobulin superfamily and is classified as a type I transmembrane protein. It is closely related to CD79A, with both proteins being essential components of the BCR complex. There are no known subtypes of CD79B, but it functions in conjunction with CD79A to mediate BCR signaling.

Function and Biological Significance

B Cell Development:

• CD79B is essential for early B cell development. It forms a complex with CD79A and associates with the pre-B cell receptor (pre-BCR) during the early stages of B cell maturation. This interaction is critical for the selection and expansion of pre-B cells, ensuring the development of functional B cells.

Antigen Recognition and Signal Transduction:

• CD79B plays a key role in antigen recognition and signal transduction. Upon antigen binding to the BCR, the ITAMs in the intracellular domain of CD79B are phosphorylated. This phosphorylation event triggers a cascade of signaling pathways, including the activation of Syk kinase, which further propagates the signal leading to B cell activation.

B Cell Activation and Proliferation:

• The signaling pathways activated by CD79B phosphorylation result in the activation of transcription factors, cytokine production, and the clonal expansion of B cells. This process is vital for mounting an effective immune response against pathogens.

Role in Immune Responses:

• CD79B, as part of the BCR complex, is involved in both T cell-dependent and T cell-independent immune responses. In T cell-dependent responses, CD79B signaling helps in the formation of germinal centers where B cells undergo somatic hypermutation and class-switch recombination. In T cell-independent responses, CD79B can directly activate B cells in response to specific antigens.

Clinical Issues

Immunodeficiencies:

• Mutations or deficiencies in CD79B can lead to primary immunodeficiencies characterized by impaired B cell development and function. Patients with CD79B deficiencies may present with hypogammaglobulinemia, recurrent infections, and an inability to mount effective antibody responses.

Autoimmune Diseases:

• Dysregulation of CD79B signaling has been implicated in autoimmune diseases. Aberrant activation of B cells through the BCR complex can contribute to the production of autoantibodies, leading to conditions such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).

Lymphomas and Leukemias:

• CD79B is expressed in various B cell malignancies, including B cell lymphomas and leukemias. The expression of CD79B is often used as a diagnostic marker in the immunophenotyping of these malignancies. Moreover, CD79B signaling pathways are potential therapeutic targets in the treatment of B cell cancers.

Therapeutic Targeting:

• CD79B has emerged as a target for novel therapeutic strategies. Antibody-drug conjugates (ADCs) targeting CD79B, such as polatuzumab vedotin, have shown promising results in the treatment of B cell lymphomas. These therapies aim to deliver cytotoxic agents directly to malignant B cells, minimizing damage to healthy tissues.

Summary

CD79B is a critical component of the B cell receptor complex, playing a vital role in B cell development, activation, and signaling. Its structure includes an extracellular domain for antigen binding, a transmembrane domain for complex formation, and an intracellular domain with ITAMs for signal transduction. CD79B is essential for initiating signaling cascades that lead to B cell activation, proliferation, and differentiation. Dysregulation of CD79B can result in immunodeficiencies, autoimmune diseases, and B cell malignancies, making it a significant focus for clinical research and therapeutic development. Understanding the molecular mechanisms of CD79B and its role in B cell biology provides valuable insights for the development of targeted therapies for various immune-related conditions.