Enforcement of γδ-lineage commitment by the pre-T-cell receptor in precursors with weak γδ-TCR signals.
Developing thymocytes bifurcate from a bipotent precursor into αβ- or γδ-lineage T cells. Considering this common origin and the fact that the T-cell receptor (TCR) β-, γ-, and δ-chains simultaneously rearrange at the double negative (DN) stage of development, the possibility exists that a given DN cell can express and transmit signals through both the pre-TCR and γδ-TCR. Here, we tested this scenario by defining the differentiation outcomes and criteria for lineage choice when both TCR-β and γδ-TCR are simultaneously expressed in Rag2(-/-) DN cells via retroviral transduction. Our results showed that Rag2(-/-) DN cells expressing both TCRs developed along the γδ-lineage, down-regulated CD24 expression, and up-regulated CD73 expression, showed a γδ-biased gene-expression profile, and produced IFN-γ in response to stimulation. However, in the absence of Inhibitor of DNA-binding 3 expression and strong γδ-TCR ligand, γδ-expressing cells showed a lower propensity to differentiate along the γδ-lineage. Importantly, differentiation along the γδ-lineage was restored by pre-TCR coexpression, which induced greater down-regulation of CD24, higher levels of CD73, Nr4a2, and Rgs1, and recovery of functional competence to produce IFN-γ. These results confirm a requirement for a strong γδ-TCR ligand engagement to promote maturation along the γδ T-cell lineage, whereas additional signals from the pre-TCR can serve to enforce a γδ-lineage choice in the case of weaker γδ-TCR signals. Taken together, these findings further cement the view that the cumulative signal strength sensed by developing DN cells serves to dictate its lineage choice.
Department of Immunology, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada M4N 3M5.
Payam
P
Zarin
Gladys W
GW
Wong
Mahmood
M
Mohtashami
David L
DL
Wiest
Juan Carlos
JC
Zúñiga-Pflücker
D000818:Animals; D002454:Cell Differentiation / Q000276:immunology*; D019070:Cell Lineage / Q000276:immunology; D004268:DNA-Binding Proteins / Q000235:genetics; D005434:Flow Cytometry; D016013:Likelihood Functions; D051379:Mice; D018345:Mice, Knockout; D060888:Real-Time Polymerase Chain Reaction; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000166:cytology*; D060168:Thymocytes / Q000276:immunology*
D004268:DNA-Binding Proteins; C499308:Rag2 protein, mouse; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta
Notch; T-cell development; β-selection; γδ T-lineage