Seroatlas · Human Serome Atlas

CD33

Myeloid cell surface antigen CD33

Also known as: CD33_HUMAN, FLJ00391, p67, SIGLEC-3, SIGLEC3

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession
P20138
Gene
CD33
Ensembl
ENSG00000105383
Chromosome
19
Canonical length
364 aa
Protein class
CD markers, FDA approved drug targets, Plasma proteins, Predicted membrane proteins
Subcellular location
Plasma membrane,Cytosol
Quaternary structure
Homodimer

OverviewNCBI Gene

Enables protein phosphatase binding activity; protein tyrosine phosphatase activator activity; and sialic acid binding activity. Involved in several processes, including immune response-regulating signaling pathway; negative regulation of cytokine production; and negative regulation of monocyte activation. Located in Golgi apparatus; external side of plasma membrane; and peroxisome. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

364 residues, UniProt reviewed canonical sequence.

>P20138|CD33
     1  MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTFFHPIPYY DKNSPVHGYW
    61  FREGAIISRD SPVATNKLDQ EVQEETQGRF RLLGDPSRNN CSLSIVDARR RDNGSYFFRM
   121  ERGSTKYSYK SPQLSVHVTD LTHRPKILIP GTLEPGHSKN LTCSVSWACE QGTPPIFSWL
   181  SAAPTSLGPR TTHSSVLIIT PRPQDHGTNL TCQVKFAGAG VTTERTIQLN VTYVPQNPTT
   241  GIFPGDGSGK QETRAGVVHG AIGGAGVTAL LALCLCLIFF IVKTHRRKAA RTAVGRNDTH
   301  PTTGSASPKH QKKSKLHGPT ETSSCSGAAP TVEMDEELHY ASLNFHGMNP SKDTSTEYSE
   361  VRTQ

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against CD33 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)
0.45
Highest tissue expression
31 nTPM

Expression across tissuesHPA

Tissue

  • bone marrow: 31 nTPM
  • spleen: 23 nTPM
  • lung: 12 nTPM
  • appendix: 11 nTPM
  • lymph node: 9.5 nTPM
  • adipose tissue: 7.4 nTPM

Single-cell type

  • kupffer cells: 196 nCPM
  • hofbauer cells: 121 nCPM
  • monocytes: 79 nCPM
  • cdc: 69 nCPM
  • monocyte progenitors: 54 nCPM
  • macrophages: 53 nCPM

Immune cell

  • myeloid DC: 214 nTPM
  • classical monocyte: 167 nTPM
  • intermediate monocyte: 122 nTPM
  • total PBMC: 78 nTPM
  • non-classical monocyte: 58 nTPM
  • neutrophil: 21 nTPM

Brain region

  • white matter: 7.6 nTPM
  • medulla oblongata: 5.4 nTPM
  • choroid plexus: 5 nTPM
  • thalamus: 4.8 nTPM
  • pons: 4.1 nTPM
  • spinal cord: 3.9 nTPM

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)
1.32
gnomAD pLI
0
gnomAD missense Z
-0.14
DepMap mean gene effect
-0.02
DepMap dependency class
selective

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

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of CD33 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads CD33 as an antibody target. Whether an autoantibody or antibody against CD33 could matter depends on whether native CD33 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

CD33 is annotated at the cell surface, where native CD33 is exposed to circulating antibodies and is a prime autoantibody target that could block, deplete, or overstimulate it.

Annotation status

The present source text does not explicitly label CD33 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/CD33. Study-independent annotations aggregated from UniProt, Human Protein Atlas, PubMed, IEDB, Pfam, InterPro, Gene Ontology, AlphaFold, gnomAD, DepMap, ClinVar, TCGA. Catalog release seroatlas-reviewed-human-uniprot-20260313.

Seroatlas is the reference for exploring autoantibody and antibody serology at the human-protein level: the autoreactome and human serome, multiplex serology (HuProt, HuScan, VirScan, PhIP-Seq).

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