C4B Gene: Complement Component 4B
Key player in the classical and lectin complement pathways, with copy number variation linked to immune disorders.
Gene Information Card
| Symbol | C4B |
|---|---|
| Full Name | complement component 4B (Chido blood group) |
| Gene Type | protein coding |
| Chromosomal Location | 6p21.33 |
| NCBI Gene ID | 721 ncbi.nlm.nih.gov/gene/721 |
| Ensembl ID | ENSG00000224389 |
| UniProt ID | P0C0L5 |
| OMIM ID | 120820 |
| HGNC ID | 1324 |
| Aliases | C4B1, C4B2, C4B_2, C4B3, C4B5, CH, CO4 |
Description
The C4B gene encodes complement component 4B, a key protein of the classical and lectin complement pathways. C4B is cleaved into C4b, which participates in opsonization and immune complex clearance. The gene is highly polymorphic and exhibits copy number variation, with low copy number associated with increased risk of systemic lupus erythematosus (SLE). C4B also carries the Chido/Rodgers blood group antigens.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Systemic lupus erythematosus | Low C4B copy number reduces complement-mediated clearance of immune complexes, promoting tissue deposition and inflammation. | ClinVar, OMIM |
| Complement component 4B deficiency | Homozygous or compound heterozygous deletions/point mutations lead to absent or dysfunctional C4B protein, impairing complement activation. | OMIM, ClinVar |
| Age-related macular degeneration | Variants in complement genes including C4B may alter complement regulation in the retina. | NCBI Gene, ClinVar |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 12.3 | High |
| Plasma | 8.7 | Medium |
| Kidney | 5.1 | Low |
| Lung | 4.2 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HepG2 | 15.6 | Hepatocyte cell line, high expression |
| THP-1 | 6.8 | Monocyte cell line, moderate expression |
| A549 | 3.2 | Lung epithelial cell line, low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| C4B*Q0 | Copy number variation (deletion) | Variable (population-dependent) | Complete deficiency of C4B protein |
| c.331C>T (p.Arg111*) | Nonsense | Rare | Premature stop, loss of function |
| c.838G>A (p.Gly280Arg) | Missense | Rare | Reduced C4B activity |
Mutation functional classification
Loss of Function (LOF)
C4B*Q0 (null allele) and nonsense mutations (e.g., p.Arg111*) result in complete loss of C4B protein function, impairing complement activation.
Gain of Function (GOF)
No well-characterized gain-of-function mutations reported for C4B.
Dominant Negative (DN)
No dominant-negative mutations described for C4B.
View complete mutation data：
Gene Ontology (GO)
| • complement activation (GO:0006956) | • complement activation (GO:0006958) |
| • opsonization (GO:0001869) | • extracellular region (GO:0005576) |
| • extracellular space (GO:0005615) |
Pathways
• Complement cascade (classical pathway)
• Complement cascade (lectin pathway)
• Immune system (Reactome R-HSA-168256)
Protein Summary
Complement component 4B (C4B) is a 1744-amino-acid glycoprotein synthesized primarily in the liver and secreted into plasma. It is cleaved by C1s into C4a and C4b; C4b covalently attaches to target surfaces, facilitating opsonization and formation of the C3 convertase. C4B is one of the most polymorphic human proteins, with copy number variation affecting complement activity and disease susceptibility.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| C4BPA Knockout HEK293 Cell Line | EDJ-KQ3252 | Human | 722 | Details Get a Quote |
| C4BPB Knockout HEK293 Cell Line | EDJ-KQ4158 | Human | 725 | Details Get a Quote |
| LRRC4B Knockout HEK293 Cell Line | EDJ-KQ11271 | Human | 94030 | Details Get a Quote |
| C4B_2 Knockout HEK293 Cell Line | EDJ-KQ12617 | Human | 100293534 | Details Get a Quote |
| C4BPA Knockout A-549 Cell Line | EDJ-KQ24790 | Human | 722 | Details Get a Quote |
| C4BPB Knockout A-549 Cell Line | EDJ-KQ26598 | Human | 725 | Details Get a Quote |
| C4BPB Knockout HeLa Cell Line | EDJ-KQ26599 | Human | 725 | Details Get a Quote |
| C4B_2 Knockout A-549 Cell Line | EDJ-KQ41670 | Human | 100293534 | Details Get a Quote |
| C4B_2 Knockout HCT 116 Cell Line | EDJ-KQ41671 | Human | 100293534 | Details Get a Quote |
| C4B_2 Knockout HeLa Cell Line | EDJ-KQ41672 | Human | 100293534 | Details Get a Quote |
| C4B Knockout HEK293 Cell Line | EDJ-KQ50166 | Human | 721 | Details Get a Quote |
| C4B Knockout HeLa Cell Line | EDJ-KQ52746 | Human | 721 | Details Get a Quote |
| C4BPA Knockout HeLa Cell Line | EDJ-KQ52747 | Human | 722 | Details Get a Quote |
| LRRC4B Knockout HeLa Cell Line | EDJ-KQ57877 | Human | 94030 | Details Get a Quote |
| C4B Knockout A-549 Cell Line | EDJ-KQ61218 | Human | 721 | Details Get a Quote |
Displaying Records 1 To 15 Of 20 Records
