title: CD28 expression redefines thymocyte development during the pre-T to DP transition.
abstract: CD27 and CD28 have emerged as indicators demarcating the transition of thymocytes through beta-selection. We found that CD28 exhibits a greater dynamic range of expression during this phase, thus it was employed to further parse the DN/CD44(-) compartment in order to assess IL-7 signaling during the beta-selection process. Plotting CD28 versus CD25 expression revealed six DN/CD44(-) populations. OP9-DL1 stromal cell co-culture was used to demonstrate a developmental linkage from DN3a (CD25(+)CD28(-/lo)) to DN3b (CD25(+)CD28(+)) to DN3c (CD25(int)CD28(+)) to DN4a (CD25(-)CD28(+)) to double positive (DP) and showed the DN4b (CD25(-)CD28(hi)) and DN4c (CD25(-)CD28(-/lo)) populations to be inefficient in producing DP cells. Using CD69 as an additional marker to further parse the DN4a population, we found the pre-DP cells to be the CD44(-)CD25(-)CD28(int)CD69(-)CD4(-/lo)CD8(-/lo) subset. Using this refined developmental scheme, IL-7R alpha expression was found to be transiently up-regulated post-beta-selection in the DN3b and DN3c subsets; however, this increase did not confer enhanced responsiveness over that observed in the DN3a population. CD28 messenger RNA expression was up-regulated in post-beta-selected cells, whereas transcripts for CD27, IL-7R alpha and Bcl-2 were lower than that observed in the DN3a population. This study refines the current thymocyte differentiation scheme to allow for more detailed evaluation of events controlling early T-cell development, specifically surrounding the beta-selection checkpoint.
authors.affiliation: Department of Surgery, University of Oklahoma College of Medicine, Tulsa, OK 74135, USA.
authors.forename: T Kent
authors.initials: TK
authors.lastname: Teague
authors.forename: Chibing
authors.initials: C
authors.lastname: Tan
authors.forename: Julie H
authors.initials: JH
authors.lastname: Marino
authors.forename: Brenda K
authors.initials: BK
authors.lastname: Davis
authors.forename: Ashlee A
authors.initials: AA
authors.lastname: Taylor
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Huey
authors.forename: C Justin
authors.initials: CJ
authors.lastname: Van De Wiele
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics; D018106:CD28 Antigens / Q000235:genetics* / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D018920:Coculture Techniques; D005434:Flow Cytometry; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D053645:Interleukin-2 Receptor alpha Subunit / Q000235:genetics / Q000276:immunology; D037181:Lectins, C-Type / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000235:genetics; D020395:Receptors, Interleukin-7 / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018106:CD28 Antigens; D053645:Interleukin-2 Receptor alpha Subunit; D037181:Lectins, C-Type; D012333:RNA, Messenger; D020395:Receptors, Interleukin-7; D000099192:CD69 Antigens; C415350:interleukin-7 receptor, alpha chain