title: Conversion of CD4+ CD25- cells into CD4+ CD25+ regulatory T cells in vivo requires B7 costimulation, but not the thymus.
abstract: The CD4+ CD25+ regulatory T cells play a critical role in controlling autoimmunity, but little is known about their development and maintenance. In this study, we investigated whether CD4+ CD25- cells can convert to CD4+ CD25+ regulatory T cells in vivo under natural conditions. CD4+ CD25- cells from CD45.1+ mice were sorted and transferred into congenic CD45.2+ mice. Converted CD4+ CD25+ cells could be detected in lymphoid organs as early as 1 wk after transfer and by 6 wk after transfer, 5-12% of transferred CD4+ cells expressed CD25. Converted CD4+ CD25+ cells themselves failed to proliferate after stimulation, but could suppress proliferation of responder cells in vitro, and also expressed high levels of Foxp3 mRNA. In addition, CD4+ CD25- cells transferred into thymectomized congenic mice converted to CD4+ CD25+ cells that also suppressed responder cell proliferation in vitro, and expressed high levels of Foxp3 mRNA. Finally, CD4+ CD25- cells transferred into B7-/- mice failed to convert into CD4+ CD25+ cells that exhibit the regulatory phenotype. These data indicate that CD4+ CD25- cells convert into CD4+ CD25+ regulatory T cells spontaneously in vivo and suggest that this conversion process could contribute significantly to the maintenance of the peripheral CD4+ CD25+ regulatory T cell population.
authors.affiliation: Department of Microbiology and Immunology, University of Louisville Health Science Center, Louisville, KY 40202, USA.
authors.forename: Shuang
authors.initials: S
authors.lastname: Liang
authors.forename: Pascale
authors.initials: P
authors.lastname: Alard
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Sarah
authors.initials: S
authors.lastname: Parnell
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Clark
authors.forename: Michele M
authors.initials: MM
authors.lastname: Kosiewicz
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D001327:Autoimmune Diseases / Q000276:immunology / Q000517:prevention & control*; D018122:B7-1 Antigen / Q000276:immunology / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors; D008221:Lymphoid Tissue / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D015375:Receptors, Interleukin-2 / Q000276:immunology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism
chemical_list: D018122:B7-1 Antigen; D017931:DNA Primers; D004268:DNA-Binding Proteins; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D015375:Receptors, Interleukin-2