CD5 (protein)

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Protein CD5 (PBB).jpg
Available structures
PDB Ortholog search: PDBe RCSB
Aliases CD5, LEU1, T1, CD5 molecule
External IDs OMIM: 153340 MGI: 88340 HomoloGene: 7260 GeneCards: 921
RNA expression pattern
PBB GE CD5 206485 at tn.png
More reference expression data
Species Human Mouse
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC) Chr 11: 61.1 – 61.13 Mb Chr 19: 10.72 – 10.74 Mb
PubMed search [1] [2]
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CD5 is a cluster of differentiation ,found on a subset of IgM-secreting B cells called B-1 cells[clarification needed], and also on T cells.[3] B-1 cells have limited diversity of their B-cell receptor due to their lack of the enzyme terminal deoxynucleotidyl transferase (TdT) and are potentially self-reactive. CD5 serves to mitigate activating signals from the BCR so that the B-1 cells can only be activated by very strong stimuli (such as bacterial proteins) and not by normal tissue proteins. CD5 was used as a T-cell marker until monoclonal antibodies against CD3 were developed.

In humans, the gene is located on the long arm of chromosome 11. There is no confirmed ligand for CD5 but there is evidence that CD72, a C-type lectin, may be a ligand or that CD5 may be homophilic, binding CD5 on the surface of other cells.[4]

T cells express higher levels of CD5 than B cells. CD5 is upregulated on T cells upon strong activation. In the thymus, there is a correlation with CD5 expression and strength of the interaction of the T cell towards self-peptides.


CD5 is a good immunohistochemical marker for T-cells, although not as sensitive as CD3. About 76% of T-cell neoplasms are reported to express CD5, and it is also found in chronic lymphocytic leukemia and mantle cell lymphoma cells. It is commonly lost in cutaneous T-cell lymphoma, and its absence can be used as an indicator of malignancy in this condition. The absence of CD5 in T cell acute lymphoblastic leukemia, while relatively rare, is associated with a poor prognosis.[5]


  1. ^ "Human PubMed Reference:". 
  2. ^ "Mouse PubMed Reference:". 
  3. ^ "Entrez Gene: CD5 CD5 molecule". 
  4. ^ Brown MH, Lacey E (Nov 15, 2010). "A ligand for CD5 is CD5". Journal of Immunology. doi:10.4049/jimmunol.0903823. PMID 20952682. 
  5. ^ Leong, Anthony S-Y; Cooper, Kumarason; Leong, F Joel W-M (2003). Manual of Diagnostic Cytology (2 ed.). Greenwich Medical Media, Ltd. pp. 67–68. ISBN 1-84110-100-1. 

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