Involvement of the TCR Cbeta FG loop in thymic selection and T cell function.
The asymmetric disposition of T cell receptor (TCR) Cbeta and Calpha ectodomains creates a cavity with a side-wall formed by the rigid Cbeta FG loop. To investigate the significance of this conserved structure, we generated loop deletion (betaDeltaFG) and betawt transgenic (tg) mice using the TCR beta subunit of the N15 CTL. N15betawt and N15betaDeltaFG H-2(b) animals have comparable numbers of thymocytes in S phase and manifest developmental progression through the CD4(-)CD8(-) double-negative (DN) compartment. N15betaDeltaFG facilitates transition from DN to CD4(+)8(+) double-positive (DP) thymocytes in recombinase activating gene (RAG)-2(-/-) mice, showing that pre-TCR function remains. N15betaDeltaFG animals possess approximately twofold more CD8(+) single-positive (SP) thymocytes and lymph node T cells, consistent with enhanced positive selection. As an altered Valpha repertoire observed in N15betaDeltaFG mice may confound the deletion's effect, we crossed N15alphabeta TCR tg RAG-2(-/-) with N15betaDeltaFG tg RAG-2(-/-) H-2(b) mice to generate N15alphabeta RAG-2(-/-) and N15alphabeta.betaDeltaFG RAG-2(-/-) littermates. N15alphabeta.betaDeltaFG RAG-2(-/-) mice show an 8-10-fold increase in DP thymocytes due to reduced negative selection, as evidenced by diminished constitutive and cognate peptide-induced apoptosis. Compared with N15alphabeta, N15alphabeta.betaDeltaFG T cells respond poorly to cognate antigens and weak agonists. Thus, the Cbeta FG loop facilitates negative selection of thymocytes and activation of T cells.
Sasada
Tetsuro
T
Laboratory of Immunobiology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115.
Touma
Maki
M
Chang
Hsiu-Ching
HC
Clayton
Linda K
LK
Wang
Jia-huai
JH
Reinherz
Ellis L
EL
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002417:Cattle; D002455:Cell Division; D019070:Cell Lineage; D016207:Cytokines / Q000378:metabolism; D004285:Dogs; D005434:Flow Cytometry; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D008198:Lymph Nodes / Q000166:cytology; D051379:Mice; D008822:Mice, Transgenic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011817:Rabbits; D051381:Rats; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology
D016207:Cytokines; D016693:Receptors, Antigen, T-Cell, alpha-beta; D007371:Interferon-gamma