A timeline demarcating two waves of clonal deletion and Foxp3 upregulation during thymocyte development.
Thymocytes that bind strongly to self-antigens are prevented from becoming naive T cells by several mechanisms. They undergo clonal deletion at two stages of development; wave 1 in immature thymocytes lacking the medulla-homing chemokine receptor, CCR7, or wave 2 in more mature CCR7(+) thymocytes. Alternatively, self-reactive thymocytes upregulate Foxp3 to become T-regulatory cells. Here, we describe the differential timing of the two waves of deletion and Foxp3 upregulation relative to the immature proliferating stage. Proliferating thymocytes were pulse-labeled in normal C57BL/6 mice with 5-ethynyl-2'-deoxyuridine (EdU). Thymocytes progressed into wave 1 (CCR7(-)) and wave 2 (CCR7(+)) of clonal deletion ~2 and 5 days after proliferation, respectively. Foxp3 upregulation occurred between 4 and 8 days after proliferation, predominantly in thymocytes with a Helios(+) CCR7(+) phenotype. These findings establish a timeline that suggests that wave 1 of clonal deletion occurs in the thymic cortex, whereas wave 2 and Foxp3 upregulation both occur in the thymic medulla.
Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
Daniel Y
DY
Hu
Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
Jin Y
JY
Yap
Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
Rushika C
RC
Wirasinha
Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
Debbie R
DR
Howard
Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
Christopher C
CC
Goodnow
Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
Stephen R
SR
Daley
D000818:Animals; D001324:Autoantigens / Q000276:immunology; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D060966:Clonal Selection, Antigen-Mediated; D004268:DNA-Binding Proteins / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D054400:Receptors, CCR7 / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D060168:Thymocytes / Q000276:immunology*; D013950:Thymus Gland / Q000033:anatomy & histology / Q000276:immunology*; D014157:Transcription Factors / Q000378:metabolism; D015854:Up-Regulation
D001324:Autoantigens; C515370:CCR7 protein, human; D004268:DNA-Binding Proteins; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D054400:Receptors, CCR7; D014157:Transcription Factors; C491746:Zfpn1a2 protein, mouse