CD22

Protein identityUniProt · HPA

UniProt accession

P20273

Gene

CD22

Ensembl

ENSG00000012124

Chromosome

19

Canonical length

847 aa

Protein class

CD markers, FDA approved drug targets, Plasma proteins, Predicted intracellular proteins, Predicted membrane proteins

OverviewNCBI Gene

Predicted to enable CD4 receptor binding activity; protein phosphatase binding activity; and sialic acid binding activity. Involved in B cell activation; negative regulation of B cell receptor signaling pathway; and regulation of endocytosis. Located in early endosome and recycling endosome. Implicated in diffuse large B-cell lymphoma. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

847 residues, UniProt reviewed canonical sequence.

>P20273|CD22
     1  MHLLGPWLLL LVLEYLAFSD SSKWVFEHPE TLYAWEGACV WIPCTYRALD GDLESFILFH
    61  NPEYNKNTSK FDGTRLYEST KDGKVPSEQK RVQFLGDKNK NCTLSIHPVH LNDSGQLGLR
   121  MESKTEKWME RIHLNVSERP FPPHIQLPPE IQESQEVTLT CLLNFSCYGY PIQLQWLLEG
   181  VPMRQAAVTS TSLTIKSVFT RSELKFSPQW SHHGKIVTCQ LQDADGKFLS NDTVQLNVKH
   241  TPKLEIKVTP SDAIVREGDS VTMTCEVSSS NPEYTTVSWL KDGTSLKKQN TFTLNLREVT
   301  KDQSGKYCCQ VSNDVGPGRS EEVFLQVQYA PEPSTVQILH SPAVEGSQVE FLCMSLANPL
   361  PTNYTWYHNG KEMQGRTEEK VHIPKILPWH AGTYSCVAEN ILGTGQRGPG AELDVQYPPK
   421  KVTTVIQNPM PIREGDTVTL SCNYNSSNPS VTRYEWKPHG AWEEPSLGVL KIQNVGWDNT
   481  TIACAACNSW CSWASPVALN VQYAPRDVRV RKIKPLSEIH SGNSVSLQCD FSSSHPKEVQ
   541  FFWEKNGRLL GKESQLNFDS ISPEDAGSYS CWVNNSIGQT ASKAWTLEVL YAPRRLRVSM
   601  SPGDQVMEGK SATLTCESDA NPPVSHYTWF DWNNQSLPYH SQKLRLEPVK VQHSGAYWCQ
   661  GTNSVGKGRS PLSTLTVYYS PETIGRRVAV GLGSCLAILI LAICGLKLQR RWKRTQSQQG
   721  LQENSSGQSF FVRNKKVRRA PLSEGPHSLG CYNPMMEDGI SYTTLRFPEM NIPRTGDAES
   781  SEMQRPPPDC DDTVTYSALH KRQVGDYENV IPDFPEDEGI HYSELIQFGV GERPQAQENV
   841  DYVILKH

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against CD22 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability

Cell surface

Secreted

No

Transmembrane segments

1

Mean surface accessibility (rSASA)

0.37

Highest tissue expression

215 nTPM

Expression across tissuesHPA

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about CD22.

Disease | AutoantibodyPubMed

Conditions in which antibodies against CD22 are reported. Each links to that disease's full target list.

• Lupus Erythematosus, Systemic 6

ReferencesPubMed · IEDB

Publications for CD22 from three distinct lines of evidence, kept separate because they answer different questions: whether antibodies are directed at the protein, whether a B-cell epitope has been mapped on it, and whether a T-cell epitope has. Each is labelled with its source.

Sources: PubMed — antigen-level antibody evidence from a custom retrieval. Records matching a controlled set of autoantibody terms (the MeSH descriptors Autoantibodies and Autoantigens, with title and abstract term variants) were obtained through NCBI E-utilities, and their titles and abstracts parsed for constructions that direct an antibody at a named protein rather than for co-occurrence. Captured names were resolved against UniProt nomenclature and each antigen adjudicated individually against the source text. IEDB — curated epitope assays from the Immune Epitope Database (Vita et al., Nucleic Acids Research 2019). Bibliographic records from PubMed and MeSH, U.S. National Library of Medicine; citation metrics from NIH iCite (Hutchins et al., PLoS Biology 2016). Titles link to PubMed; abstracts are not reproduced here. The NLM does not endorse this analysis.

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance)

0.35

gnomAD pLI

0.8

gnomAD missense Z

0.67

DepMap mean gene effect

-0.04

DepMap dependency class

none

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 3% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

• B cell activation
• cell adhesion
• negative regulation of B cell receptor signaling pathway
• negative regulation of calcium-mediated signaling
• negative regulation of immunoglobulin production
• regulation of B cell proliferation
• regulation of endocytosis
• regulation of immune response

Molecular functions

• carbohydrate binding
• CD4 receptor binding
• IgM binding
• protein phosphatase binding
• sialic acid binding
• signaling receptor binding

Cellular components

• cell surface
• cytoplasm
• early endosome
• external side of plasma membrane
• extracellular exosome
• membrane
• neuronal cell body membrane
• plasma membrane
• recycling endosome

Protein domainsUniProt · Pfam · InterPro

• Immunoglobulin subtype 2
• Immunoglobulin domain subtype
• Immunoglobulin-like domain
• CD80-like, immunoglobulin C2-set
• Immunoglobulin-like fold
• Immunoglobulin-like domain superfamily
• CD80-like C2-set immunoglobulin domain
• Immunoglobulin domain
• Immunoglobulin domain
• B-cell receptor CD22, first Ig-like domain
• B-cell receptor CD22-like, first Ig-like

KeywordsUniProt

• Cell adhesion
• Cell membrane
• Disulfide bond
• Glycoprotein
• Immunoglobulin domain
• Isopeptide bond
• Lectin
• Membrane
• Phosphoprotein
• Repeat
• Signal
• Transmembrane
• Transmembrane helix

InteractionsUniProt · HPA

Protein binding partners of CD22 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

• GRB2
• INPP5D
• LYN
• SYK
• PTPN6