Cell surface antigen CD5 is a marker for activated human B cells.
CD5 is a T-cell associated marker that is also expressed by two B-cell neoplasms; lymphocytic leukemia and mantle cell lymphoma. CD5 antigen is expressed in 95% of thymocytes and 72% of peripheral blood lymphocytes. In lymph nodes, CD5 is mainly reactive with Tcells. It has been shown to react with thymic carcinomas, but rarely in thymomas. It has also been observed in a subset of intravascular large B-cell lymphomas and marks some anaplastic large cell lymphomas. CD5 has proven very useful in marking mantle cell lymphoma when used in tandem with CD23, cyclin D1, and CD10 (CD10 is negative; CD5, cyclin D1 are positive for mantle cell lymphoma).
CD5 is a negative regulator of B-cell receptor (BCR) signaling that is up-regulated after BCR stimulation and likely contributes to B-cell tolerance in vivo. However, CD5 is constitutively expressed on the B-1 subset of B cells. Contrary to CD5(-) B-2 B cells, B-1 B cells are long-lived because of autocrine interleukin-10 (IL-10) production through unknown mechanisms. We demonstrate herein a direct relationship between CD5 expression and IL-10 production. Human peripheral blood CD5(+) B cells produce more IL-10 than CD5(-) B cells after BCR activation. Introducing CD5 into CD5(-) B cells induces the production of IL-10 by activating its promoter and the synthesis of its mRNA. The cytoplasmic domain of CD5 is sufficient for this process. CD5 also protects normal human B cells from apoptosis after BCR stimulation while reducing the BCR-induced Ca(2+) response. We conclude that CD5 supports the survival of B cells by stimulating IL-10 production and by concurrently exerting negative feedback on BCR-induced signaling events that can promote cell death.
References:
Werner-Favre C, Vischer TL, Wohlwend D, Zubler RH. Cell surface antigen CD5 is a marker for activated human B cells. Eur J Immunol. 1989 Jul;19(7):1209-13. doi: 10.1002/eji.1830190709. PMID: 2474446.
Gary-Gouy H, Harriague J, Bismuth G, Platzer C, Schmitt C, Dalloul AH. Human CD5 promotes B-cell survival through stimulation of autocrine IL-10 production. Blood. 2002 Dec 15;100(13):4537-43. doi: 10.1182/blood-2002-05-1525. Epub 2002 Aug 8. PMID: 12393419.
CD 5
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