CD5 (protein)

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CD5 molecule
Protein CD5 (PBB).jpg
PDB rendering based on 2ja4.
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols CD5 ; LEU1; T1
External IDs OMIM153340 MGI88340 HomoloGene7260 GeneCards: CD5 Gene
RNA expression pattern
PBB GE CD5 206485 at tn.png
More reference expression data
Species Human Mouse
Entrez 921 12507
Ensembl ENSG00000110448 ENSMUSG00000024669
UniProt P06127 P13379
RefSeq (mRNA) NM_014207 NM_007650
RefSeq (protein) NP_055022 NP_031676
Location (UCSC) Chr 11:
60.87 – 60.9 Mb
Chr 19:
10.72 – 10.74 Mb
PubMed search [1] [2]

CD5 is a cluster of differentiation found on a subset of IgM-secreting B cells called B-1 cells, and also on T cells.[1] 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 ligand confirmed, even if CD72, a C-type lectin, may be considered a probable ligand.

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, hairy cell 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.[2]


  1. ^ "Entrez Gene: CD5 CD5 molecule". 
  2. ^ 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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