CR2

Chr 1q32.2

complement C3d receptor 2

Aliases:: CD21, C3DR
MANE:: ENST00000367057.8

OMIM: 120650 ↗NCBI: 1380 ↗Ensembl ↗

Annotations refreshed 9 hours ago.

Predicted protein structure

AlphaFold predicted structure

CR2 · P20023

v62025-08-01

Predicted Aligned Error matrix for CR2 — diagonal shows residue index, colour shows pairwise prediction confidence (lower is better) — Predicted Aligned Error

Mean pLDDT

74.9/ 100

Confident

1,033 residues

Confidence breakdown

Very high(≥ 90)2%
Confident(70–90)71%
Low(50–70)21%
Very low(< 50)6%

Open interactive 3D viewer

AlphaFold (Jumper et al., 2021) · CC BY 4.0

Clinical relevance (Genomics England PanelApp)

Diagnostic Grade (Green)

COVID-19 research
BIALLELIC, autosomal or pseudoautosomal
Primary immunodeficiency or monogenic inflammatory bowel disease
BIALLELIC, autosomal or pseudoautosomal

Disease associations (Open Targets)

immunodeficiency, common variable, 7
0.75
common variable immunodeficiency
0.48
systemic lupus erythematosus
0.47
Recurrent infections
0.37
recurrent infections associated with rare immunoglobulin isotypes deficiency
0.37
immunodeficiency, common variable, 2
0.33
urolithiasis
0.30
alcohol drinking
0.30
frozen shoulder
0.28
hereditary disease
0.19

Score is the Open Targets composite evidence score (0-1). Higher = stronger gene-disease association.

Protein function (UniProt)

Complement receptor type 2

Serves as a receptor for various ligands including complement component CD3d, HNRNPU OR IFNA1 (PubMed:1849076, PubMed:21527715, PubMed:7753047). When C3d is bound to antigens, attaches to C3d on B-cell surface and thereby facilitates the recognition and uptake of antigens by B-cells (PubMed:21527715). This interaction enhances B-cell activation and subsequent immune responses. Forms a complex with several partners on the surface of B-cells including CD19, FCRL5 and CD81, to form the B-cell coreceptor complex that plays a crucial role in B-cell activation and signaling (PubMed:1383329, PubMed:30107486). Also induces specific intracellular signaling separately from the BCR and CD19 by activating the tyrosine kinase SRC, which then phosphorylates nucleolin/NCL and triggers AKT and GSK3 kinase activities in a SYK/CD19-independent manner (PubMed:12938232). Acts as a ligand for CD23 (FcepsilonRII), a low-affinity receptor for IgE, which is expressed on B-cells and other immune cells, and thus participates in the regulation of IgE production (PubMed:1386409)