| Property | Value |
|----------|-------|
| Gene Symbol | TNFRSF13C |
| Full Name | TNF Receptor Superfamily Member 13C |
| Alternative Names | BAFFR, BR3, CD268 |
| Chromosomal Location | 22q12.1 |
| NCBI Gene ID | 115650 |
| OMIM | 606269 |
| Ensembl ID | ENSG00000159958 |
| UniProt ID | Q9Y239 |
| Gene Family | TNF receptor superfamily |
| Associated Diseases | MS, Autoimmune Encephalitis, Neuroinflammatory Disorders |
| Property | Value |
|----------|-------|
| Gene Symbol | TNFRSF13C |
| Full Name | TNF Receptor Superfamily Member 13C |
| Alternative Names | BAFFR, BR3, CD268 |
| Chromosomal Location | 22q12.1 |
| NCBI Gene ID | 115650 |
| OMIM | 606269 |
| Ensembl ID | ENSG00000159958 |
| UniProt ID | Q9Y239 |
| Gene Family | TNF receptor superfamily |
| Associated Diseases | MS, Autoimmune Encephalitis, Neuroinflammatory Disorders |
<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">BAFFR (TNFRSF13C)</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>TNFRSF13C (BAFFR)</td></tr>
<tr><td><strong>Full Name</strong></td><td>TNF Receptor Superfamily Member 13C</td></tr>
<tr><td><strong>Chromosome</strong></td><td>22q12.1</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[115650](https://www.ncbi.nlm.nih.gov/gene/115650)</td></tr>
<tr><td><strong>OMIM</strong></td><td>606269</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>[ENSG00000159958](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000159958)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q9Y239](https://www.uniprot.org/uniprot/Q9Y239)</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>MS, Autoimmune Encephalitis, Neuroinflammatory Disorders</td></tr>
</table>
</div>
BAFFR (B cell Activating Factor Receptor, also known as TNFRSF13C, BR3, or CD268) is a critical member of the TNF receptor superfamily that plays an essential and non-redundant role in B cell survival, maturation, and homeostasis. Encoded by the TNFRSF13C gene on chromosome 22q12.1, BAFFR is expressed almost exclusively on B cells and is the sole receptor that mediates the survival and maturation functions of BAFF (B cell Activating Factor, also known as TNFSF13B or BLyS). Unlike TACI (TNFRSF13B) and BCMA (TNFRSF17), which also bind BAFF, BAFFR is uniquely required for the development and maintenance of mature B cells.
The discovery of BAFFR's essential role in B cell biology came from studies of A/WySnJ mice, which carry a natural mutation in the Tnfrsf13c gene and exhibit profound B cell deficiency. This demonstrated that BAFFR is the critical receptor for BAFF-mediated survival signals, without which peripheral B cells undergo apoptosis. In humans, BAFFR deficiency causes severe antibody deficiency, highlighting its indispensable role in humoral immunity.
Beyond its well-established role in B cell biology, BAFFR has emerging relevance in neuroinflammatory and neurodegenerative diseases. B cells and antibodies are prominent features of central nervous system (CNS) autoimmune diseases, and BAFFR-expressing B cells likely contribute to disease pathogenesis through autoantibody production, cytokine secretion, and antigen presentation. Elevated BAFF levels have been detected in the cerebrospinal fluid (CSF) and brain tissue of patients with multiple sclerosis (MS), autoimmune encephalitis, and other neuroinflammatory conditions.
The TNFRSF13C gene spans approximately 7.5 kilobases and consists of 5 exons encoding the BAFFR protein. The gene is located on chromosome 22q12.1, a region not within the major histocompatibility complex (MHC), distinguishing it from many other immune-related genes.
The BAFFR protein is a type I transmembrane receptor with the following structural features:
Extracellular Domain: The extracellular region of BAFFR contains a single cysteine-rich domain (CRD) characteristic of TNF receptor family members, but notably simpler than TACI or other family members. This single CRD is sufficient for high-affinity BAFF binding. The extracellular domain forms a trimer, allowing binding to the trimeric BAFF ligand.
Transmembrane Domain: A single pass transmembrane helix anchors the receptor in the cell membrane.
Cytoplasmic Domain: The intracellular region is relatively short and contains motifs that mediate interactions with TRAF (TNF Receptor-Associated Factor) proteins, particularly TRAF3. Unlike TACI, BAFFR lacks a canonical TRAF-binding motif but still recruits TRAF proteins to activate downstream signaling.
BAFFR is unique among BAFF receptors in that it does not bind APRIL (A Proliferation-Inducing Ligand), which binds to TACI and BCMA. This ligand specificity contributes to BAFFR's unique functional role in B cell survival.
BAFFR activation triggers several downstream signaling cascades:
BAFFR signaling activates both canonical and non-canonical NF-κB pathways:
Canonical NF-κB: BAFFR engagement recruits TRAF proteins (primarily TRAF3) to the receptor complex, leading to activation of the IKK complex and subsequent IκB degradation. This releases NF-κB dimers (p50/p65, p50/c-Rel) to translocate to the nucleus and induce expression of survival genes including Bcl-2 and Bcl-xL.
Non-canonical NF-κB: BAFFR activates NF-κB-inducing kinase (NIK), which phosphorylates IKKα, leading to p100 processing to p52 and subsequent RelB activation. This pathway is particularly important for mature B cell survival.
TRAF3 is a critical adaptor in BAFFR signaling. Under resting conditions, TRAF3 binds to BAFFR and promotes its degradation, limiting baseline NF-κB activation. Upon BAFF binding, TRAF3 is recruited and degraded, relieving this inhibition and allowing sustained NF-κB signaling.
BAFFR can activate the Akt/mTOR pathway, which promotes cell survival and protein synthesis necessary for B cell maintenance.
BAFFR is expressed almost exclusively on B cells:
In the CNS, BAFFR is primarily expressed on:
BAFFR is absolutely essential for the survival of mature peripheral B cells. The BAFF/BAFFR axis provides critical survival signals that:
BAFFR is required for the progression of transitional B cells to mature naive B cells. BAFFR signaling supports:
BAFFR plays important roles in the germinal center reaction:
BAFFR is required for optimal antibody responses:
MS is an autoimmune demyelinating disease characterized by inflammation, demyelination, and neurodegeneration in the CNS. B cells and antibodies are central to MS pathogenesis, as evidenced by:
Autoimmune encephalitis is a group of disorders characterized by autoantibodies against neuronal surface antigens, leading to brain inflammation and dysfunction.
BAFFR in AE:
BAFFR plays roles in various neuroinflammatory conditions:
Emerging evidence suggests BAFF/BAFFR involvement in neurodegenerative diseases:
While both BAFFR and TACI bind BAFF, they have distinct and non-overlapping functions:
| Feature | BAFFR | TACI |
|---------|-------|------|
| Ligand specificity | BAFF only | BAFF and APRIL |
| Essential for B cell survival | Yes | No |
| Role in class switching | Important | Critical |
| Expression | B cells only | B cells, T cells, others |
| Signaling | TRAF3-dependent | TRAF-dependent |
| Disease associations | B cell deficiency | CVID, autoimmunity |
BAFFR is the primary receptor for B cell survival, while TACI is more important for class switching and plasma cell function. Both receptors can contribute to disease when dysregulated.
Several therapeutic approaches target this pathway:
BAFF inhibitors:
In neuroinflammatory diseases:
The following diagram shows the key molecular relationships involving BAFFR Gene (TNFRSF13C) discovered through SciDEX knowledge graph analysis: