Details for: C1QB

Gene ID: 713

Gene Type:  Protein-coding  - A gene that serves as a template for producing a messenger RNA (mRNA) molecule, which is then translated into a functional protein.

Symbol: C1QB

Ensembl ID: ENSG00000173369

Description: complement C1q B chain

Selected Context(s):  Overall

Cell Significance Landscape

Contexts:

Associated with

Significant Cells

Cell Significance Index (CSI) scores for the chosen context(s)

  • myeloid leukocyte CL0000766
    CSI 57.42
    rCSI 52.97%
    PRS 96.4
  • elicited macrophage CL0000861
    CSI 52.76
    rCSI 48.45%
    PRS 97.96
  • alternatively activated macrophage CL0000890
    CSI 49.96
    rCSI 62.81%
    PRS 98.34
  • CD14-low, CD16-positive monocyte CL0002396
    CSI 42.54
    rCSI 32.77%
    PRS 97.45
  • alveolar macrophage CL0000583
    CSI 39.09
    rCSI 64.39%
    PRS 96.29
  • CD1c-positive myeloid dendritic cell CL0002399
    CSI 35.8
    rCSI 43.24%
    PRS 97.85
  • CD14-positive, CD16-positive monocyte CL0002397
    CSI 30.31
    rCSI 39.71%
    PRS 98.59
  • macrophage CL0000235
    CSI 28.34
    rCSI 51.55%
    PRS 95.4
  • lung macrophage CL1001603
    CSI 26.07
    rCSI 58.23%
    PRS 98.08
  • mononuclear phagocyte CL0000113
    CSI 24.21
    rCSI 53.3%
    PRS 96.99
  • Kupffer cell CL0000091
    CSI 23.31
    rCSI 53.31%
    PRS 96.14
  • inflammatory macrophage CL0000863
    CSI 21.92
    rCSI 37.45%
    PRS 99.31
  • Hofbauer cell CL3000001
    CSI 20.04
    rCSI 37.83%
    PRS 97.84
  • monocyte CL0000576
    CSI 17.46
    rCSI 31.57%
    PRS 96.15
  • intermediate monocyte CL0002393
    CSI 17.3
    rCSI 26.11%
    PRS 97.83
  • mature T cell CL0002419
    CSI 16.57
    rCSI 12.89%
    PRS 98.82
  • dendritic cell CL0000451
    CSI 16.25
    rCSI 20.02%
    PRS 94.55
  • myeloid dendritic cell CL0000782
    CSI 15.74
    rCSI 22.8%
    PRS 99.05
  • colon macrophage CL0009038
    CSI 14.53
    rCSI 67.14%
    PRS 98.76
  • bronchus fibroblast of lung CL2000093
    CSI 14.18
    rCSI 11.52%
    PRS 95.18
  • lung interstitial macrophage CL4033043
    CSI 13.63
    rCSI 30.59%
    PRS 98.99
  • Langerhans cell CL0000453
    CSI 13.55
    rCSI 20.69%
    PRS 98.37
  • glial cell CL0000125
    CSI 13.33
    rCSI 50.77%
    PRS 90.69
  • mast cell CL0000097
    CSI 12.38
    rCSI 26.73%
    PRS 92.18
  • kidney interstitial alternatively activated macrophage CL1000695
    CSI 11.23
    rCSI 29.26%
    PRS 96.53
  • promyelocyte CL0000836
    CSI 9.75
    rCSI 14.06%
    PRS 96.11
  • fibroblast of lung CL0002553
    CSI 9.62
    rCSI 8.96%
    PRS 96.35
  • microglial cell CL0000129
    CSI 9.39
    rCSI 37.81%
    PRS 94.22
  • epithelial cell of lower respiratory tract CL0002632
    CSI 8.93
    rCSI 6.93%
    PRS 96.7
  • neutrophil CL0000775
    CSI 8.88
    rCSI 49.66%
    PRS 92.97
  • pulmonary artery endothelial cell CL1001568
    CSI 8.72
    rCSI 11.86%
    PRS 97.51
  • epithelial cell of lung CL0000082
    CSI 8.39
    rCSI 6.96%
    PRS 96.25
  • central nervous system macrophage CL0000878
    CSI 7.61
    rCSI 25.24%
    PRS 96.25
  • alveolar adventitial fibroblast CL4028006
    CSI 6.58
    rCSI 10.4%
    PRS 96.16
  • tissue-resident macrophage CL0000864
    CSI 6.43
    rCSI 30.07%
    PRS 98.78
  • lung ciliated cell CL1000271
    CSI 6.33
    rCSI 7.31%
    PRS 91.52
  • metallothionein-positive alveolar macrophage CL4033042
    CSI 5.4
    rCSI 58.71%
    PRS 98.42
  • hepatic stellate cell CL0000632
    CSI 5.36
    rCSI 20.09%
    PRS 93.14
  • tracheobronchial smooth muscle cell CL0019019
    CSI 5.24
    rCSI 9.24%
    PRS 96.83
  • mature microglial cell CL0002629
    CSI 4.93
    rCSI 20.47%
    PRS 94.05
  • vascular associated smooth muscle cell CL0000359
    CSI 4.86
    rCSI 15.75%
    PRS 94.38
  • multi-ciliated epithelial cell CL0005012
    CSI 4.47
    rCSI 4.46%
    PRS 91.24
  • endothelial cell of pericentral hepatic sinusoid CL0019022
    CSI 3.83
    rCSI 11.8%
    PRS 96.05
  • dendritic cell, human CL0001056
    CSI 3.73
    rCSI 5.73%
    PRS 98.24
  • periportal region hepatocyte CL0019026
    CSI 3.53
    rCSI 13.72%
    PRS 91.93
  • exhausted T cell CL0011025
    CSI 2.53
    rCSI 42.88%
    PRS 96.55
  • kidney resident macrophage CL1000698
    CSI 2.53
    rCSI 50.41%
    PRS 99.09
  • mesothelial cell CL0000077
    CSI 2.29
    rCSI 8.95%
    PRS 84.74
  • microcirculation associated smooth muscle cell CL0008035
    CSI 2.17
    rCSI 6.29%
    PRS 94.78
  • endothelial cell of placenta CL0009092
    CSI 2.16
    rCSI 10.62%
    PRS 96.77
  • myeloid dendritic cell, human CL0001057
    CSI 0.98
    rCSI 5.53%
    PRS 98.89
  • CD8-positive, alpha-beta memory T cell, CD45RO-positive CL0001203
    CSI 0.96
    rCSI 1.16%
    PRS 79.05

Cell ID: Standard Cell Ontology term used for mapping and comparing cells across experiments. Ensures consistency in analyzing cellular functions across tissues.
Fold Change: Represents the ratio of the current Cell Significance Index to the Cell Significance Index Threshold, indicating how much the gene expression has changed compared to a baseline.
Cell Significance Index: Reflects how strongly a gene is expressed in this specific cell.

Cell ID: Standard Cell Ontology term used for mapping and comparing cells across experiments. Ensures consistency in analyzing cellular functions across tissues.
Fold Change: Represents the ratio of the current Cell Significance Index to the Cell Significance Index Threshold, indicating how much the gene expression has changed compared to a baseline.
Cell Significance Index: Reflects how strongly a gene is expressed in this cell type. Calculated using techniques like effect size estimation and bootstrapping for reliability.

Cell ID: Standard Cell Ontology term used for mapping and comparing cells across experiments. Ensures consistency in analyzing cellular functions across tissues.
Fold Change: Represents the ratio of the current Cell Significance Index to the Cell Significance Index Threshold, indicating how much the gene expression has changed compared to a baseline.
Cell Significance Index: Reflects how strongly a gene is expressed in this cell type. Calculated using techniques like effect size estimation and bootstrapping for reliability.
Network Configuration

Explore relationships of the current gene. Select an Interaction Source: 'ONTOLOGY' for shared pathways (GO/Reactome) or 'STRING' for protein-protein interactions. Further refine by selecting context genes and comparing Cell Significance Index (CSI) scores between baseline and target cell types and their specific contexts.

Comma-separated if multiple.
Comma-separated if multiple.
Legend:
  • Query Gene
  • Node Color (Target Cell CSI, relative to current network):
    • Very High
    • High
    • Medium
    • Low
    • Very Low
    • CSI N/A
  • Node Size: Proportional to Target Cell CSI magnitude
  • STRING PPI Edge
  • Shared Pathway Edge (ONTOLOGY)

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Other Information

This section provides additional information about the gene, including a description generated by an AI language model and details about associated proteins.

## Summary [C1QB](/details-gene/713) (complement C1q B chain) is a protein-coding gene located on chromosome 1 that encodes a crucial component of the C1q complex. This complex is the recognition molecule of the classical complement pathway, a fundamental arm of the [innate immune system](/details-pathway/R-HSA-168249). The C1q complex, composed of A, B, and C chains, binds to antigen-antibody complexes, initiating a proteolytic cascade that leads to pathogen opsonization, inflammation, and cell lysis. Expression data reveals that [C1QB](/details-gene/713) is a defining feature of the mononuclear phagocyte system, with exceptionally high significance in various subsets of [macrophages](/details-cell/CL0000235) and [monocytes](/details-cell/CL0000576). Deficiencies in C1q components are associated with a high risk of developing severe autoimmune diseases, such as systemic lupus erythematosus ([OMIM:120570](https://omim.org/entry/120570)). ## Cellular Roles and Expression Landscape **Overall**, the expression profile of [C1QB](/details-gene/713) demonstrates its highly specialized role as a key product of the myeloid lineage. The gene's significance is highest in [myeloid leukocyte](/details-cell/CL0000766) populations, underpinning its central function in innate immunity. Its expression is particularly prominent across the macrophage spectrum. [C1QB](/details-gene/713) shows very high cell significance index (CSI) scores in specialized tissue-resident and elicited macrophages, including [elicited macrophage](/details-cell/CL0000861) (CSI: 52.76), [alternatively activated macrophage](/details-cell/CL0000890) (CSI: 49.96), [alveolar macrophage](/details-cell/CL0000583) (CSI: 39.09), [Kupffer cell](/details-cell/CL0000091) (CSI: 23.31), and [Hofbauer cell](/details-cell/CL3000001) (CSI: 20.04). This suggests that C1q production is a core function of macrophages in diverse anatomical locations, from the lung and liver to the placenta. Furthermore, [C1QB](/details-gene/713) is a significant marker for circulating [monocytes](/details-cell/CL0000576) and their subsets, such as [CD14-low, CD16-positive monocyte](/details-cell/CL0002396) (CSI: 42.54) and [CD14-positive, CD16-positive monocyte](/details-cell/CL0002397) (CSI: 30.31). Its high expression is also observed in professional antigen-presenting cells like the [CD1c-positive myeloid dendritic cell](/details-cell/CL0002399) (CSI: 35.80). The consistent high significance across these cell types establishes [C1QB](/details-gene/713) as a constitutive and fundamental component of the cellular machinery of the mononuclear phagocyte system, responsible for initiating humoral innate immune responses. ## Pathways and Molecular Function The molecular functions and biological pathways associated with [C1QB](/details-gene/713) are highly consistent with its expression pattern in myeloid cells. As an integral part of the [complement component c1q complex](/details-ontology/GO:0062167), its primary role is in the [innate immune response](/details-ontology/GO:0045087) ([Link](https://pubmed.ncbi.nlm.nih.gov/3000358/)). Specifically, it is a key initiator of the [classical antibody-mediated complement activation](/details-pathway/R-HSA-173623), one of the three main pathways of the [complement cascade](/details-pathway/R-HSA-166658). This process begins when the globular heads of the C1q complex bind to the Fc region of immunoglobulins (IgM or IgG) that are bound to antigens, or directly to pathogen surfaces and apoptotic cells. Beyond its canonical immune function, GO annotations suggest a role for [C1QB](/details-gene/713) in neural development and maintenance through its involvement in [synapse pruning](/details-ontology/GO:0098883) and its localization to the [postsynapse](/details-ontology/GO:0098794). This function is primarily executed by microglia (the resident macrophages of the central nervous system) and is critical for refining neural circuits. This dual role in both systemic immunity and CNS homeostasis highlights the functional versatility of the C1q complex in processes of recognition and elimination of unwanted structures, be they pathogens, immune complexes, or supernumerary synapses. ## Research Directions The specific expression of [C1QB](/details-gene/713) in diverse macrophage subtypes, including both inflammatory and alternatively activated phenotypes, suggests its regulation and function are context-dependent and may influence macrophage polarization and effector functions. ### Proposed Hypotheses 1. **Hypothesis:** The expression level of [C1QB](/details-gene/713), and consequently the local concentration of secreted C1q, is a critical modulator of macrophage polarization. High C1q levels in the microenvironment may promote an anti-inflammatory, pro-phagocytic phenotype specialized for clearing apoptotic cells and debris, whereas lower levels may permit a more pro-inflammatory response. 2. **Hypothesis:** Beyond classical complement activation, C1q produced by peripheral tissue macrophages, such as [Kupffer cells](/details-cell/CL0000091) or [alveolar macrophages](/details-cell/CL0000583), engages in "synapse pruning-like" functions by tagging damaged cells or extracellular matrix components for clearance, thereby contributing to tissue homeostasis and remodeling after injury. ### Experimental Approach To test the hypothesis that [C1QB](/details-gene/713) modulates macrophage polarization, an *in vitro* experiment could be conducted. Primary human monocytes could be differentiated into macrophages and subsequently polarized towards an M1 (pro-inflammatory) state with LPS and IFN-γ or an M2 (anti-inflammatory) state with IL-4 and IL-13. [C1QB](/details-gene/713) expression would be knocked down using CRISPR-Cas9 or siRNA in a subset of these cells. The effect of [C1QB](/details-gene/713) depletion on polarization would be assessed by measuring the expression of canonical M1/M2 marker genes (e.g., *TNF*, *IL6*, *ARG1*, *MRC1*) via qPCR or RNA-seq, and by functional assays assessing phagocytosis of apoptotic cells and cytokine secretion profiles via ELISA. ### Therapeutic Potential [C1QB](/details-gene/713) represents a complex but potentially valuable therapeutic target. Given that C1q deficiency is strongly linked to autoimmunity due to impaired clearance of immune complexes and apoptotic bodies ([Link](https://doi.org/10.1016/s0171-2985(98)80033-8/)), systemic inhibition of C1QB is likely to be detrimental. However, targeted **inhibition** of C1q activity in specific pathological contexts, such as in antibody-mediated autoimmune diseases (e.g., lupus nephritis) or ischemia-reperfusion injury where complement activation drives tissue damage, could be beneficial. Conversely, strategies for the targeted **activation** or delivery of the C1q complex could be explored as a therapy to enhance the clearance of cellular debris in conditions characterized by defective phagocytosis. Its high specificity to myeloid cells suggests that therapies targeting C1q-producing cells could potentially limit off-target effects compared to systemic complement inhibitors.

Genular Protein ID: 1102049999

Symbol: C1QB_HUMAN

Name: Complement C1q subcomponent subunit B

UniProtKB Accession Codes:

P02746 Q5T959 Q96H17

Database IDs:

AGR 1 AlphaFoldDB 1 BioGRID 1 BioGRID-ORCS 1 BioMuta 1 CORUM 1 CPTAC 1 CTD 1 ChiTaRS 1 ComplexPortal 1 DMDM 1 DNASU 1 DisGeNET 1 DrugBank 9 EMBL 4 EMDB 1 EvolutionaryTrace 1 GO 12 Gene3D 1 GeneCards 1 GenomeRNAi 1 HGNC 1 InParanoid 1 IntAct 1 InterPro 4 KEGG 1 MIM 3 MINT 1 MalaCards 1 MassIVE 1 NCBI Taxonomy 1 Orphanet 1 OrthoDB 1 PANTHER 2 PDB 9 PDBsum 9 PIR 1 PRINTS 1 PRO 1 PROSITE 1 PathwayCommons 1 PaxDb 1 PeptideAtlas 1 Pfam 2 PharmGKB 1 Pharos 1 PhosphoSitePlus 1 PhylomeDB 1 Proteomes 1 ProteomicsDB 1 RNAct 1 Reactome 3 RefSeq 2 SASBDB 1 SIGNOR 1 SMART 1 SMR 1 STRING 1 SUPFAM 1 SignaLink 1 TreeFam 1 UCSC 1 UniProtKB 1 eggNOG 1 iPTMnet 1 jPOST 1 neXtProt 1

Citations:

PubMed ID: 16710414

Title: The DNA sequence and biological annotation of human chromosome 1.

PubMed ID: 16710414

DOI: 10.1038/nature04727

PubMed ID: 15489334

Title: The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

PubMed ID: 15489334

DOI: 10.1101/gr.2596504

PubMed ID: 3000358

Title: Molecular cloning and characterization of the complementary DNA and gene coding for the B-chain of subcomponent C1q of the human complement system.

PubMed ID: 3000358

DOI: 10.1042/bj2310729

PubMed ID: 708376

Title: Amino acid sequence of the N-terminal 108 amino acid residues of the B chain of subcomponent C1q of the first component of human complement.

PubMed ID: 708376

DOI: 10.1042/bj1730863

PubMed ID: 486087

Title: Complete amino acid sequences of the three collagen-like regions present in subcomponent C1q of the first component of human complement.

PubMed ID: 486087

DOI: 10.1042/bj1790367

PubMed ID: 6981411

Title: Completion of the amino acid sequences of the A and B chains of subcomponent C1q of the first component of human complement.

PubMed ID: 6981411

DOI: 10.1042/bj2030559

PubMed ID: 6208566

Title: Cloning and characterization of the complementary DNA for the B chain of normal human serum C1q.

PubMed ID: 6208566

DOI: 10.1098/rstb.1984.0095

PubMed ID: 12847249

Title: Modular organization of the carboxyl-terminal, globular head region of human C1q A, B, and C chains.

PubMed ID: 12847249

DOI: 10.4049/jimmunol.171.2.812

PubMed ID: 19006321

Title: Interaction of human C1q with IgG and IgM: revisited.

PubMed ID: 19006321

DOI: 10.1021/bi801131h

PubMed ID: 6286235

Title: Comparable content of hydroxylysine-linked glycosides in subcomponents C1q of the first component of human, bovine and mouse complement.

PubMed ID: 6286235

DOI: 10.1016/s0174-173x(81)80015-5

PubMed ID: 12960167

Title: The crystal structure of the globular head of complement protein C1q provides a basis for its versatile recognition properties.

PubMed ID: 12960167

DOI: 10.1074/jbc.m307764200

PubMed ID: 9777412

Title: Molecular basis of hereditary C1q deficiency.

PubMed ID: 9777412

DOI: 10.1016/s0171-2985(98)80033-8

PubMed ID: 9476130

Title: Molecular basis of a new type of C1q-deficiency associated with a non-functional low molecular weight (LMW) C1q: parallels and differences to other known genetic C1q-defects.

PubMed ID: 9476130

DOI: 10.1016/s0162-3109(97)00065-9

PubMed ID: 16959974

Title: The consensus coding sequences of human breast and colorectal cancers.

PubMed ID: 16959974

DOI: 10.1126/science.1133427

Sequence Information:

  • Length: 253
  • Mass: 26722
  • Checksum: D80C753C0D430EDC
  • Sequence:
    • MMMKIPWGSI PVLMLLLLLG LIDISQAQLS CTGPPAIPGI PGIPGTPGPD GQPGTPGIKG 
EKGLPGLAGD HGEFGEKGDP GIPGNPGKVG PKGPMGPKGG PGAPGAPGPK GESGDYKATQ 
KIAFSATRTI NVPLRRDQTI RFDHVITNMN NNYEPRSGKF TCKVPGLYYF TYHASSRGNL 
CVNLMRGRER AQKVVTFCDY AYNTFQVTTG GMVLKLEQGE NVFLQATDKN SLLGMEGANS 
IFSGFLLFPD MEA