CR2 (Complement C3d Receptor 2)
CD21, Complement Receptor Type 2
Gene Information Card
| Symbol | CR2 |
|---|---|
| Full Name | Complement C3d Receptor 2 |
| Gene Type | protein-coding |
| Chromosomal Location | 1q32.2 |
| NCBI Gene ID | 1380 ncbi.nlm.nih.gov/gene/1380 |
| Ensembl ID | ENSG00000117322 |
| UniProt ID | P20023 |
| OMIM ID | 120650 |
| HGNC ID | 2336 |
| Aliases | CD21, C3DR, CR2, complement receptor type 2, Epstein-Barr virus receptor |
Description
The CR2 gene encodes complement receptor type 2 (CD21), a membrane protein expressed on mature B cells, follicular dendritic cells, and some T cells. It binds complement fragments iC3b, C3dg, and C3d, and serves as the receptor for Epstein-Barr virus (EBV). CR2 forms a complex with CD19 and CD81 to modulate B cell activation and immune response. Mutations in CR2 are associated with immunodeficiency and systemic lupus erythematosus.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Immunodeficiency, common variable, 7 (CVID7) | Loss-of-function mutations impair B cell activation and antibody production | ClinVar, OMIM |
| Systemic lupus erythematosus (SLE) | Defective clearance of immune complexes due to reduced CR2 expression | ClinVar, OMIM |
| Epstein-Barr virus infection | CR2 serves as the primary receptor for EBV entry into B cells | UniProt, NCBI |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Spleen | 12.5 | High |
| Lymph node | 10.2 | High |
| Bone marrow | 6.8 | Medium |
| Blood | 5.1 | Medium |
| Lung | 0.9 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| Raji (Burkitt lymphoma) | 15.3 | High CR2 expression |
| Daudi (Burkitt lymphoma) | 14.1 | High CR2 expression |
| K562 (leukemia) | 0.2 | Very low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.172C>T (p.Arg58*) | Nonsense | Rare | Loss of function; associated with CVID7 |
| c.442G>A (p.Gly148Ser) | Missense | Rare | Impaired C3d binding; linked to SLE |
| c.1000C>T (p.Arg334Cys) | Missense | Rare | Reduced surface expression; immunodeficiency |
Mutation functional classification
Loss of Function (LOF)
Nonsense and missense mutations that reduce CR2 expression or ligand binding lead to impaired B cell activation and immune deficiency (e.g., CVID7).
Gain of Function (GOF)
No confirmed gain-of-function mutations reported in CR2.
Dominant Negative (DN)
No dominant-negative mutations described for CR2.
View complete mutation data：
Gene Ontology (GO)
| • complement receptor activity | • virus receptor activity |
| • B cell receptor signaling pathway | • innate immune response |
| • cell surface receptor signaling pathway |
Pathways
• Complement cascade (Reactome: R-HSA-166658)
• B cell receptor signaling (Reactome: R-HSA-983705)
• Epstein-Barr virus infection (KEGG: hsa05169)
Protein Summary
CR2 (CD21) is a 145 kDa type I transmembrane glycoprotein composed of 15-16 short consensus repeats (SCRs) in its extracellular domain. It binds complement fragments iC3b, C3dg, and C3d, and serves as the receptor for Epstein-Barr virus (EBV). CR2 forms a signaling complex with CD19 and CD81 on B cells, lowering the threshold for B cell activation. It is also expressed on follicular dendritic cells, where it retains immune complexes to facilitate antigen presentation. Mutations in CR2 cause common variable immunodeficiency type 7 (CVID7) and increase susceptibility to systemic lupus erythematosus.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| CR2 Knockout HEK293 Cell Line | EDJ-KQ3812 | Human | 1380 | Details Get a Quote |
| CR2 Knockout HCT 116 Cell Line | EDJ-KQ25941 | Human | 1380 | Details Get a Quote |
| CR2 Knockout HeLa Cell Line | EDJ-KQ52975 | Human | 1380 | Details Get a Quote |
| CR2 Knockout A-549 Cell Line | EDJ-KQ61442 | Human | 1380 | Details Get a Quote |
