title: T-cell proliferation and forkhead box P3 expression in human T cells are dependent on T-cell density: physics of a confined space?
abstract: T-cell proliferation rates in vitro depend on factors including initial T-cell number, dose of stimulus, culture time, and available physical space. The role of forkhead box P3 (FoxP3) in the identification of T cells with a regulatory phenotype remains controversial in humans. Through 5-carboxyfluorescein diacetate succinimidyl ester labeling of human T cells and subsequent culture of different numbers of T cells and antigen-presenting cells (APC), we studied proliferative T-cell responses and FoxP3 expression in divided T cells. T-cell proliferation rates depended on initial T-cell/APC numbers. Proliferation rates decreased when high initial T-cell numbers were increased. FoxP3 expression was expressed exclusively in virtually all divided T cells cultured at high T-cell densities, irrespective of their CD4 nature or cytokine content, and was coexpressed with T-bet. However, when T cells were cultured on larger surfaces or at lower initial numbers, FoxP3 expression was not induced in divided T cells, even when most of the cells had undergone cell division. FoxP3(+) T cells generated at high cell densities did not elicit a suppressive phenotype and FoxP3 expression was subsequently lost in time when the stimulus was removed. Therefore, caution should be observed in the use of FoxP3 expression to identify regulatory T cells in humans because its expression may be only a consequence of activation status in a restricted environment.
authors.affiliation: Antigen, Presentation Research Group, Imperial College London, Northwick Park and St. Mark's Campus, Harrow, HA1 3UJ, UK.
authors.forename: David
authors.initials: D
authors.lastname: Bernardo
authors.forename: Hafid O
authors.initials: HO
authors.lastname: Al-Hassi
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Mann
authors.forename: Cheng T
authors.initials: CT
authors.lastname: Tee
authors.forename: Aravinth U
authors.initials: AU
authors.lastname: Murugananthan
authors.forename: Simon T C
authors.initials: ST
authors.lastname: Peake
authors.forename: Ailsa L
authors.initials: AL
authors.lastname: Hart
authors.forename: Stella C
authors.initials: SC
authors.lastname: Knight
mesh_terms: D000938:Antigen-Presenting Cells / Q000473:pathology; D002452:Cell Count; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D060833:Cellular Microenvironment / Q000276:immunology; D018920:Coculture Techniques; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D007108:Immune Tolerance; D008213:Lymphocyte Activation; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D000098815:T-bet Transcription Factor
chemical_list: C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D020825:T-Box Domain Proteins; D000098815:T-bet Transcription Factor