Affinage

KEL

Kell blood group glycoprotein · UniProt P23276

Length
732 aa
Mass
82.8 kDa
Annotated
2026-06-10
55 papers in source corpus 18 papers cited in narrative 18 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

KEL encodes the Kell glycoprotein, a type II transmembrane red-cell protein that functions as an endothelin-3-converting enzyme (ECE-3) and forms a disulfide-linked complex with the integral membrane protein XK (PMID:11132157). Genetic disruption of Kell abolishes this enzymatic activity, reduces XK protein levels without altering XK mRNA, and increases Gardos channel activity while blunting the normal endothelin-3-mediated enhancement of that channel, linking Kell catalytic function to red-cell ion transport (PMID:19544475). The interdependence of the two loci is reciprocal: near-total loss of Kell antigens arises when reduced KEL antigen alleles combine with an XK splice-site mutation, establishing that XK governs surface Kell antigen expression (PMID:8916972). KEL transcription is driven by GATA1 and KLF1, which co-occupy its promoter and are required for KEL expression, with natural variants in their binding motifs reducing transcription factor occupancy and KEL activity (PMID:38644556). Loss-of-function mutations cause Kell-null (Ko) and Kmod phenotypes through diverse mechanisms including splice-donor disruption that skips the transmembrane-encoding exon 3 and introduces a premature stop codon (PMID:11134029), and a synonymous exon 16 variant that triggers exon skipping (PMID:24795954), while antigen-defining missense variants map to residues such as position 193 critical for KEL1 expression (PMID:17076841). Beyond the red cell, the Kell glycoprotein is a model alloantigen: anti-KEL alloantibody responses require Type 1 interferon signaling through IFNAR1 in B cells for germinal center and plasma cell differentiation (PMID:28836263), and immunoprophylaxis acts by FcγR- and complement-dependent antigen modulation (PMID:27688803). Inflammatory and antiviral stimuli modulate this response, which can be suppressed via the Nrf2 antioxidant pathway (PMID:40235992).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2000 High

    Established the molecular identity and enzymatic function of the Kell protein, answering what biochemical activity this blood group antigen carries.

    Evidence Biochemical and enzymatic characterization of mouse Kell ortholog by Western blot, activity assay, and cDNA/genomic sequencing

    PMID:11132157

    Open questions at the time
    • In vivo physiological substrate range beyond endothelin-3 not defined
    • Structural basis of XK disulfide linkage not resolved
  2. 2000 High

    Defined a molecular mechanism for the Kell-null phenotype, showing how a splice mutation eliminates the antigen-bearing protein.

    Evidence DNA sequencing and RT-PCR of an intron 3 splice donor mutation showing exon 3 skipping and premature stop codon

    PMID:11134029

    Open questions at the time
    • Does not address the full allelic spectrum of null/mod phenotypes
  3. 2009 High

    Demonstrated in vivo that Kell catalytic activity controls red-cell ion transport and stabilizes XK, linking enzyme function to physiology.

    Evidence Murine Kel knockout with enzymatic, ion transport, protein expression, tumor, and motor function readouts

    PMID:19544475

    Open questions at the time
    • Mechanism connecting endothelin-3 conversion to Gardos channel regulation not fully traced
    • Basis of XK destabilization in Kell absence unresolved
  4. 1996 Medium

    Established the reciprocal genetic dependence between KEL and XK loci in governing surface antigen levels.

    Evidence Serology, RFLP, XK sequencing, and family study of combined Kpa homozygosity and XK splice mutation

    PMID:8916972

    Open questions at the time
    • Molecular basis of XK control over Kell surface expression not mechanistically defined
  5. 2009 Medium

    Showed antigen expression is modulated in cis by adjacent KEL alleles, refining how surface antigen quantity is set.

    Evidence Phased allele sequencing with quantitative flow cytometry of a KEL*1,3 allele

    PMID:19347978

    Open questions at the time
    • Molecular mechanism of cis-suppression unknown
  6. 2022 High

    Identified the transcriptional control of KEL, answering how erythroid-specific expression is established.

    Evidence ChIP-seq, ATAC-seq, luciferase reporter, EMSA, and mass spectrometry showing GATA1/KLF1 co-occupancy

    PMID:38644556

    Open questions at the time
    • Interplay of GATA1/KLF1 with other erythroid regulators not fully mapped
  7. 2017 High

    Defined the immune requirement for anti-KEL alloantibody formation, identifying Type 1 IFN signaling in B cells as essential.

    Evidence Murine transfusion model with IFNAR1 knockout and bone marrow chimeras with cell-specific deletion

    PMID:28836263

    Open questions at the time
    • Source and trigger of Type 1 IFN in steady-state transfusion not identified
  8. 2016 High

    Explained how anti-KEL immunoprophylaxis works, attributing protection to FcγR- and complement-dependent antigen modulation.

    Evidence Murine transfusion model with FcγR/C3 knockouts, flow cytometry, Western blot, phagocytosis assay

    PMID:27688803

    Open questions at the time
    • Relative contribution of phagocytic versus enzymatic antigen loss not separated
  9. 2025 Medium

    Identified a pathway to suppress anti-KEL alloimmunization, showing Nrf2 activation dampens IFN-stimulated responses and antibody production.

    Evidence Murine transfusion model with Nrf2 knockout and pharmacological CDDO-Im activation (preprint)

    PMID:40235992

    Open questions at the time
    • Preprint not peer-reviewed
    • Mechanistic link between Nrf2 and IFN-stimulated gene suppression incomplete

Open questions

Synthesis pass · forward-looking unresolved questions
  • How Kell endothelin-3-converting enzyme activity mechanistically couples to Gardos channel regulation and what non-erythroid physiological roles Kell serves remain open.
  • No structural model of the Kell-XK complex
  • Physiological substrates beyond endothelin-3 uncharacterized
  • Non-erythroid functions only hinted at by tumor and motor phenotypes

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016787 hydrolase activity 2 GO:0140096 catalytic activity, acting on a protein 2
Localization
GO:0005886 plasma membrane 2
Pathway
R-HSA-168256 Immune System 2 R-HSA-74160 Gene expression (Transcription) 1
Partners
GATA1KLF1XK
Complex memberships
Kell-XK complex

Evidence

Reading pass · 18 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 The mouse Kell glycoprotein (ortholog of human KEL) is a type II membrane glycoprotein with endothelin-3-converting enzyme (ECE-3) activity, disulfide-linked to the integral membrane protein XK on red blood cells. Western blot, enzymatic activity assay, Northern blot, cDNA sequencing, genomic organization analysis Immunogenetics High 11132157
2009 Targeted disruption of the murine Kel gene abolishes endothelin-3-converting enzyme activity on RBCs, reduces XK protein levels (without affecting XK mRNA), increases RBC Gardos channel activity, blunts the normal endothelin-3-mediated enhancement of Gardos channel activity, reduces intratumoral neovascularization, and mildly affects some motor activities. Homologous recombination knockout, enzymatic activity assay, Western blot, Northern blot, ion transport assay, tumor implantation model, motor function testing American journal of hematology High 19544475
2000 A G-to-C mutation at the splice donor site of intron 3 in the KEL gene causes the Kell-null (Ko) phenotype by abolishing normal splicing; the resulting major transcript skips exon 3 (which encodes the transmembrane domain), introducing a premature stop codon that prevents translation of the C-terminal segment bearing all known Kell antigen positions. DNA sequencing, RT-PCR, splice site mutation analysis The Journal of biological chemistry High 11134029
1993 The KEL gene was localized to chromosome 7q33–35 by fluorescence in situ hybridization, providing evidence that Kell antigenic determinants are encoded by the polypeptide chain rather than associated sugar molecules. Fluorescence in situ hybridization (FISH) with biotinylated KEL cDNA probe Human genetics Medium 8340113
1991 The KEL locus was genetically linked to the prolactin-inducible protein locus (PIP) and provisionally assigned to chromosome 7q32–36 by genetic linkage analysis. Genetic linkage analysis Annals of human genetics Low 1683210
1996 Near-total absence of Kell antigens can result from a combination of homozygosity for Kpa (KEL3) and a splice-site mutation in XK (intron 2), demonstrating that Kell antigen expression is partially governed by XK protein and that both loci act together to regulate surface Kell antigen levels. Serology, RFLP, XK gene sequencing, family study Blood Medium 8916972
2001 Point mutations G865A (Glu249Lys) and G863A (Arg248Gln) in adjacent codons of KEL exon 8 cause amino acid substitutions that define the RAZ and VLAN Kell blood group phenotypes, respectively. DNA sequencing of KEL open reading frame and flanking intronic regions, PCR-based genotyping assays Vox sanguinis Medium 11904003
2006 A serine at position 193 of the Kell glycoprotein (encoded by a 577A>T transversion, Ser193), distinct from the canonical Thr193Met KEL1/KEL2 polymorphism, results in expression of an abnormal KEL1 antigen in addition to KEL2, demonstrating that residue 193 is critical for KEL1 antigen expression. DNA sequencing (genomic and cDNA), flow cytometry, PCR genotyping Transfusion Medium 17076841
2008 Alternative splicing of KEL gene transcripts occurs in non-reticulocyte cells (total RNA), while reticulocytes express only one normal transcript; Kell glycoprotein is strongly expressed on RBCs but absent or very low on leukocytes. RT-PCR, nested PCR, sequencing, flow cytometry with monoclonal antibodies Chinese journal of medical genetics Medium 18841563
2009 A novel KEL*1,3 allele (KEL1 and KEL3 on the same chromosome) causes approximately 80% reduction in KEL1 surface antigen expression, demonstrating a cis-modifier effect of KEL3 on KEL1 expression. Serology, flow cytometry, PCR with sequence-specific priming, genomic DNA sequencing of separated parental alleles Transfusion Medium 19347978
2014 A synonymous mutation (c.1719C>T) in KEL exon 16 causes complete exon 16 skipping despite being located 16 bases downstream of the 3′ splice site, resulting in a null (silent) KEL allele and contributing to Kmod phenotype when combined with another mod allele. Genomic and cDNA sequencing from erythroid progenitor-derived cells, serology Vox sanguinis Medium 24795954
2022 GATA1 and KLF1 co-occupy the KEL promoter and are functionally required for KEL transcription; naturally occurring variants in their binding motifs reduce GATA1 and KLF1 binding affinity and KEL transcriptional activity. ChIP-seq, ATAC-seq, luciferase reporter assays, EMSA, mass spectrometry Transfusion High 38644556
2016 Anti-KEL immunoprophylaxis prevents alloimmunization through antigen modulation (rapid removal of detectable KEL antigen from circulating RBCs), and this process requires redundant pathways involving both Fcγ receptors and complement (C3); absence of both abolishes immunoprophylaxis efficacy and KEL antigen modulation. Murine transfusion model using transgenic KEL-expressing RBCs, FcγR/C3 knockout mice, flow cytometry, Western blot, in vitro phagocytosis assay Blood High 27688803
2017 B cells require Type 1 interferon (IFN-α/β) signaling through IFNAR1 to produce alloantibodies against the KEL glycoprotein after transfusion; IFNAR1-deficient B cells fail to differentiate into germinal center B cells and plasma cells in response to KEL-expressing RBCs. Murine transfusion model, IFNAR1 knockout mice, bone marrow chimeras with cell-specific IFNAR1 deletion, flow cytometry Transfusion High 28836263
2019 Influenza infection promotes alloimmunization to transfused KEL-expressing RBCs through a mechanism dependent on recipient Type 1 IFN production; blocking or genetic deletion of Type 1 IFN signaling significantly reduces influenza-induced anti-KEL alloantibody formation. Murine transfusion model, influenza infection, antibody blockade and genetic knockout of Type 1 IFN signaling, flow cytometric crossmatch Transfusion Medium 31403208
2020 Poly(I:C)-induced antiviral responses cause breakthrough anti-KEL alloimmunization despite immunoprophylaxis; this is associated with increased RBC consumption by inflammatory monocytes and elevated MCP-1 and IL-6; poly(I:C) can induce breakthrough alloimmunization even in recipients lacking Type 1 IFN receptors, suggesting additional IFN-independent pathways. Murine transfusion model, knockout mice (FcγR, C3, IFNAR), cytokine measurement, flow cytometry, Type 1 IFN administration Blood Medium 32266378
2022 KEL promotes cell proliferation in acute erythroleukemia cells, and its downregulation reverses drug resistance to JQ1; KEL expression is associated with gain of H3K27 acetylation and is regulated by cotranscription factors GATA1 and TAL1. Cell proliferation assay (CCK8), flow cytometry (apoptosis), ChIP-seq/epigenetic analysis, transcription factor binding analysis Oxidative medicine and cellular longevity Medium 35140839
2025 The Nrf2 activator CDDO-Im suppresses poly(I:C)-induced Type 1 IFN-stimulated gene expression and inhibits anti-KEL IgG alloantibody production after transfusion of KEL-expressing RBCs, in an Nrf2-dependent manner (no effect in Nrf2−/− mice). Murine transfusion model, Nrf2 knockout mice, pharmacological Nrf2 activation, anti-KEL IgG measurement by flow cytometry, gene expression analysis bioRxivpreprint Medium 40235992

Source papers

Stage 0 corpus · 55 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2006 KEL-8 is a substrate receptor for CUL3-dependent ubiquitin ligase that regulates synaptic glutamate receptor turnover. Molecular biology of the cell 71 16394099
2000 Differentiation of autologous ABO, RHD, RHCE, KEL, JK, and FY blood group genotypes by analysis of peripheral blood samples of patients who have recently received multiple transfusions. Transfusion 59 10960520
2013 Transfusion of murine red blood cells expressing the human KEL glycoprotein induces clinically significant alloantibodies. Transfusion 49 23621760
2013 Alloantibodies to a paternally derived RBC KEL antigen lead to hemolytic disease of the fetus/newborn in a murine model. Blood 41 23801629
2016 Antigen modulation as a potential mechanism of anti-KEL immunoprophylaxis in mice. Blood 38 27688803
2000 Molecular basis of the Kell-null phenotype: a mutation at the splice site of human KEL gene abolishes the expression of Kell blood group antigens. The Journal of biological chemistry 37 11134029
2017 B cells require Type 1 interferon to produce alloantibodies to transfused KEL-expressing red blood cells in mice. Transfusion 32 28836263
1991 Genetic linkage between the Kell blood group system and prolactin-inducible protein loci: provisional assignment of KEL to chromosome 7. Annals of human genetics 26 1683210
1979 Reverse-phase HPLC of DNA restriction fragments and ribooligonucleotides on uncoated Kel-F powder. Nucleic acids research 24 461189
2011 Identification of RHCE and KEL alleles in large cohorts of Afro-Caribbean and Comorian donors by multiplex SNaPshot and fragment assays: a transfusion support for sickle cell disease patients. British journal of haematology 23 21623766
1996 A combination of the effects of rare genotypes at the XK and KEL blood group loci results in absence of Kell system antigens from the red blood cells. Blood 23 8916972
2019 Type 1 IFN signaling critically regulates influenza-induced alloimmunization to transfused KEL RBCs in a murine model. Transfusion 18 31403208
1996 Development of a PCR-based diagnostic assay for the determination of KEL genotype in donor blood samples. Transfusion medicine (Oxford, England) 18 8809961
2006 A KEL gene encoding serine at position 193 of the Kell glycoprotein results in expression of KEL1 antigen. Transfusion 17 17076841
2002 Heterozygosity for two novel null alleles of the KEL gene causes the Kell-null phenotype in a Japanese woman. British journal of haematology 15 11918559
1999 kel-1, a novel Kelch-related gene in Caenorhabditis elegans, is expressed in pharyngeal gland cells and is required for the feeding process. Genes to cells : devoted to molecular & cellular mechanisms 14 10421842
2009 Two novel null alleles of the KEL gene detected in two Chinese women with the K(null) phenotype. Transfusion medicine (Oxford, England) 12 19747286
2000 The mouse Kell blood group gene (Kel): cDNA sequence, genomic organization, expression, and enzymatic function. Immunogenetics 12 11132157
2013 An easy and efficient strategy for KEL genotyping in a multiethnic population. Revista brasileira de hematologia e hemoterapia 10 23741186
2011 Genetic and functional analyses describe a novel 730delG mutation in the KEL gene causing K0 phenotype in a Taiwanese blood donor. Transfusion medicine (Oxford, England) 9 21707797
2009 A novel KEL*1,3 allele with weak Kell antigen expression confirming the cis-modifier effect of KEL3. Transfusion 9 19347978
2009 Changes in red cell ion transport, reduced intratumoral neovascularization, and some mild motor function abnormalities accompany targeted disruption of the Mouse Kell gene (Kel). American journal of hematology 9 19544475
2020 Poly(I:C) causes failure of immunoprophylaxis to red blood cells expressing the KEL glycoprotein in mice. Blood 8 32266378
2021 [Expression of circ-KEL in acute myeloid leukemia and its regulatory mechanisms in leukemic cells]. Zhonghua xue ye xue za zhi = Zhonghua xueyexue zazhi 7 33910309
2014 Three uncommon KEL alleles in one family with unusual Kell phenotypes explain a 35-year old conundrum. Vox sanguinis 7 24795954
1993 Regional chromosomal assignment of the Kell blood group locus (KEL) to chromosome 7q33-q35 by fluorescence in situ hybridization: evidence for the polypeptide nature of antigenic variation. Human genetics 7 8340113
1977 Enzyme polymorphisms of Ideles populations (Ahaggar, Algeria) and the Iwellemeden Kel Kummer Twaregs (Menaka, Mali). Human heredity 7 198354
2017 Silent KEL alleles identified from Japanese individuals with the Ko phenotype. Vox sanguinis 6 29280152
2013 Identification of novel silent KEL alleles causing KEL:-5 (Ko) phenotype or discordance between KEL:1,-2 phenotype/KEL*01/02 genotype. Transfusion 6 23581578
2024 Epigenetic dissection of human blood group genes reveals regulatory elements and detailed characteristics of KEL and four other loci. Transfusion 5 38644556
2022 Functional Evaluation of KEL as an Oncogenic Gene in the Progression of Acute Erythroleukemia. Oxidative medicine and cellular longevity 5 35140839
2022 Noninvasive diagnostics of fetal KEL*01.01 allele from maternal plasma of immunized women using digital PCR protocols. Transfusion 5 35191535
2018 Transfused platelets enhance alloimmune responses to transfused KEL-expressing red blood cells in a murine model. Blood transfusion = Trasfusione del sangue 5 30418129
2015 454-Sequencing™ for the KEL, JR, and LAN Blood Groups. Methods in molecular biology (Clifton, N.J.) 5 26024631
2014 Three missense mutations found in the KEL gene lead to K(mod) or K0 red blood cell phenotypes. Transfusion 5 25041236
2010 KEL*02 alleles with alterations in and around exon 8 in individuals with apparent KEL:1,-2 phenotypes. Vox sanguinis 5 20384970
2001 Point mutations in KEL exon 8 determine a high-incidence (RAZ) and a low-incidence (KEL25, VLAN) antigen of the Kell blood group system. Vox sanguinis 5 11904003
2020 Genomic analyses of KEL alleles in alloimmunized thalassemia patients from Iran. Transfusion and apheresis science : official journal of the World Apheresis Association : official journal of the European Society for Haemapheresis 4 32565058
2020 The effectiveness of KEL and RHCE fetal genotype assessment in alloimmunized women by minisequencing. Ceska gynekologie 4 33562967
2024 The Incidences of KEL Blood Group Antigens and Phenotypes in Southwestern Saudi Arabia. International journal of general medicine 3 39308969
2021 Risk Minimization of Hemolytic Disease of the Fetus and Newborn Using Droplet Digital PCR Method for Accurate Fetal Genotype Assessment of RHD, KEL, and RHCE from Cell-Free Fetal DNA of Maternal Plasma. Diagnostics (Basel, Switzerland) 3 33925253
2022 A paleoecological context to assess the development of oak forest in Colombia: A comment on Zorilla-Azcué, S., Gonzalez-Rodríguez, A., Oyama, K., González, M.A., & Rodríguez-Correa, H., The DNA history of a lonely oak: Quercus humboldtii phylogeography in the Colombian Andes. Ecology and Evolution 2021, doi: 10.100-2/ece3.7529. Ecology and evolution 2 35356589
2016 New KEL*01M and KEL*02M alleles: structural modeling to assess the impact of amino acid changes. Transfusion 2 26996808
2025 A novel homozygous KEL variant causing K0 phenotype in a Chinese woman and therapeutic plasma exchange for anti-Ku removal in preoperative management. Transfusion 1 41241849
2022 Novel KEL allele associated with loss of Kpb identified in a white blood donor. Immunohematology 1 35852066
2020 A forest-specialist carnivore in the middle of the desert?Comments on https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.5230. Ecology and evolution 1 32313639
2019 Establishment of KEL*01 and KEL*02 Genotyping to Recruit Uncommon, Kell-positive, Reagent Red Cells Among Thai Blood Donors. Clinical laboratory 1 31625357
1978 [The hypothesis of the genetic transmission (autosomal recessive) of subtypes of HBs Ag. The example of Kel Kummer]. Comptes rendus hebdomadaires des seances de l'Academie des sciences. Serie D: Sciences naturelles 1 417847
1975 The HL-A gene structure of Twareg populations. II. The Kel Dinig. Tissue antigens 1 1138437
2026 Anti-Ku alloimmunization due to a KEL*02N.19 allele causing Kell-null phenotype despite KEL*02 genotype prediction. Vox sanguinis 0 41692422
2025 CDDO-Imidazole regulates RBC alloimmunization to the KEL antigen by activating Nrf2. bioRxiv : the preprint server for biology 0 40235992
2024 Genomic analysis of KEL*03 and KEL*04 alleles among Thai blood donors. African journal of laboratory medicine 0 38629087
2022 Response to: A paleoecological context to assess the development of oak forest in Colombia: A comment on Zorrilla-Azcué, S., González-Rodríguez, A., Oyama, K., González, M.A. & Rodríguez-Correa, H., The DNA history of a lonely oak: Quercus humboldtii phylogeography in the Colombian Andes. Ecology and Evolution 2021, doi:10.1002/ece3.7529. Ecology and evolution 0 36110879
2013 [A KEL*02mod allele responsible for an apparent maternity exclusion]. Transfusion clinique et biologique : journal de la Societe francaise de transfusion sanguine 0 23727116
2008 [Different KEL gene mRNA transcripts in reticulocyte and non-reticulocyte cells]. Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 0 18841563

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