Higher Sensitivity of Foxp3+ Treg Compared to Foxp3- Conventional T Cells to TCR-Independent Signals for CD69 Induction.
T lymphocytes elicit specific responses after recognizing cognate antigen. However, antigen-experienced T cells can also respond to non-cognate stimuli, such as cytokines. CD4+ Foxp3+ regulatory T cells (Treg) exhibit an antigen-experienced-like phenotype. Treg can regulate T cell responses in an antigen-specific or bystander way, and it is still unclear as to which extent they rely on T cell receptor (TCR) signals. The study of the antigen response of Treg has been hampered by the lack of downstream readouts for TCR stimuli. Here we assess the effects of TCR signals on the expression of a classical marker of early T cell activation, CD69. Although it can be induced following cytokine exposure, CD69 is commonly used as a readout for antigen response on T cells. We established that upon in vitro TCR stimulation CD69 induction on Foxp3+ Treg cells was more dependent on signaling via soluble factors than on TCR activation. By contrast, expression of the activation marker Nur77 was only induced after TCR stimulation. Our data suggest that Treg are more sensitive to TCR-independent signals than Foxp3- cells, which could contribute to their bystander activity.
Max-Planck-Institute of Immunobiology and Epigenetics, Freiburg, Germany; Centre for Chronic Immunodeficiency (CCI), University Medical Center Freiburg, University of Freiburg, Freiburg, Germany; Faculty of Biology, University of Freiburg, Freiburg, Germany.
Anna
A
Bremser
Max-Planck-Institute of Immunobiology and Epigenetics, Freiburg, Germany; Centre for Chronic Immunodeficiency (CCI), University Medical Center Freiburg, University of Freiburg, Freiburg, Germany.
Maria
M
Brack
Max-Planck-Institute of Immunobiology and Epigenetics, Freiburg, Germany; Centre for Chronic Immunodeficiency (CCI), University Medical Center Freiburg, University of Freiburg, Freiburg, Germany.
Ana
A
Izcue
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D001854:Bone Marrow Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D037181:Lectins, C-Type / Q000378:metabolism*; D051379:Mice; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D000099192:CD69 Antigens
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D016207:Cytokines; D051858:Forkhead Transcription Factors; D037181:Lectins, C-Type; D011948:Receptors, Antigen, T-Cell; D000099192:CD69 Antigens; C498833:Foxp3 protein, mouse