title: Without peripheral interference, thymic deletion is mediated in a cohort of double-positive cells without classical activation.
abstract: Peripheral activation can cause bystander thymocyte death by eliciting a "cytokine storm." This event complicates in vivo studies using exogenous ligand-induced models of negative selection. A stable transgenic model that selectively eliminates peripheral CD4 cells has allowed us to analyze negative selection as direct cognate events in two T cell receptor transgenic mice, OT-II and DO11. Whereas cognate peptide induced a massive deletion in double-positive (DP) cells in mice with peripheral CD4 cells, this DP deletion was modest in mice lacking peripheral CD4 cells. Using BrdUrd and annexin V staining, we found that negative selection primarily occurs in a cohort of DP cells and the absence of single-positive (SP) cells is largely caused by reduction in the cohort of DP precursors. Moreover, the fates of DP cells and SP cells after antigen exposure were vastly different. Whereas SP cells up-regulated uniformly their CD69 and CD44 levels, increased their cell size, and survived after antigen exposure, DP cells had less CD69 and CD44 up-regulation, no size change, and promptly died. Thus, negative selection represents an "abortive" activation different from activation-induced cell death of mature T cells.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Melbourne 3050, Australia.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Zhan
authors.forename: Jared F
authors.initials: JF
authors.lastname: Purton
authors.forename: Dale I
authors.initials: DI
authors.lastname: Godfrey
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Cole
authors.forename: William R
authors.initials: WR
authors.lastname: Heath
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Lew
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000494:pharmacology; D000941:Antigens / Q000378:metabolism; D015703:Antigens, CD / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D017209:Apoptosis; D001973:Bromodeoxyuridine / Q000494:pharmacology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D017637:Clonal Deletion; D004396:Coloring Agents / Q000494:pharmacology; D004789:Enzyme Activation; D005434:Flow Cytometry; D018960:Hyaluronan Receptors / Q000096:biosynthesis; D016130:Immunophenotyping; D037181:Lectins, C-Type; D008024:Ligands; D008213:Lymphocyte Activation; D051379:Mice; D008822:Mice, Transgenic; D010455:Peptides / Q000737:chemistry; D013154:Spleen / Q000166:cytology; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism*; D015854:Up-Regulation; D000099192:CD69 Antigens
chemical_list: D017304:Annexin A5; D000941:Antigens; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D001973:Bromodeoxyuridine; D004396:Coloring Agents; D018960:Hyaluronan Receptors; D037181:Lectins, C-Type; D008024:Ligands; D010455:Peptides; D000099192:CD69 Antigens