title: The CD4(+)CD8(+) and CD4(+) subsets of FOXP3(+) thymocytes differ in their response to growth factor deprivation or stimulation.
abstract: The timing of thymic regulatory T (Treg) cell commitment remains unclear. Specifically, there is disagreement as to whether the CD4(+)CD8(+) FOXP3(+) thymocytes are precursors of mature CD4(+) FOXP3(+) Treg cells, or an independent Treg cell lineage. We reasoned that precursors should be more susceptible to apoptosis than mature Treg cells, and tested this by growth factor removal and anti-CD3 stimulation. Both treatments resulted in an increase of CD4(+) FOXP3(+) thymocytes, whereas the frequency of CD4(+)CD8(+) FOXP3(+) thymocytes decreased significantly. These changes were accompanied by an increase of annexin(+) apoptotic cells. Both of these FOXP3(+) subsets expressed higher levels of Bcl-2 and BIM than other thymocytes, and while in our setting expression of BIM seemed to predispose the cells to apoptosis, Bcl-2 had no apparent protective effect. These results indicate that CD4(+)CD8(+) FOXP3(+) thymocytes are more susceptible to apoptosis than mature CD4(+) FOXP3(+) Treg cells. This is consistent with the view that they are still immature and thus likely to represent a precursor population.
authors.affiliation: Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Helsinki, Finland. anni.lehtoviita@helsinki.fi
authors.forename: A
authors.initials: A
authors.lastname: Lehtoviita
authors.forename: L H
authors.initials: LH
authors.lastname: Rossi
authors.forename: E
authors.initials: E
authors.lastname: Kekäläinen
authors.forename: H
authors.initials: H
authors.lastname: Sairanen
authors.forename: T P
authors.initials: TP
authors.lastname: Arstila
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D017209:Apoptosis / Q000276:immunology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics; D000072224:Bcl-2-Like Protein 11; D017252:CD3 Complex / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology / Q000378:metabolism*; D016827:CD8 Antigens / Q000276:immunology / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D002675:Child, Preschool; D005260:Female; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics / Q000276:immunology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D036341:Intercellular Signaling Peptides and Proteins / Q000172:deficiency* / Q000494:pharmacology*; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D017252:CD3 Complex; D015704:CD4 Antigens; D016827:CD8 Antigens; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; C508017:IL2RA protein, human; D036341:Intercellular Signaling Peptides and Proteins; D053645:Interleukin-2 Receptor alpha Subunit; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2