title: Cutting edge: Paracrine, but not autocrine, IL-2 signaling is sustained during early antiviral CD4 T cell response.
abstract: IL-2 is expressed predominantly by activated T cells, and regulates T cell function by activating, via its receptor, the latent transcription factor STAT5. This signaling can occur in either a paracrine (between cells) or an autocrine (same cell) manner, although the kinetics by which these two signaling modes operate during in vivo T cell responses are unknown. In the current study, IL-2 expression and signaling in a clonotypic population of antiviral CD4+ T cells was analyzed by flow cytometry during the initial 24 h of priming. IL-2 expression and STAT5 activation peaked in parallel, but surprisingly, were almost completely mutually exclusive. Thus, only paracrine IL-2 signaling could be observed. As an additional indication of the efficiency of paracrine IL-2 signaling, polyclonal CD4+CD25+Foxp3+ regulatory T cells displayed detectable STAT5 activation under steady-state conditions, which was strongly enhanced by neighboring IL-2-expressing antiviral CD4 cells.
authors.affiliation: Center for Immunotherapy of Cancer and Infectious Diseases and Department of Immunology, University of Connecticut Health Center, Farmington, CT 06030, USA.
authors.forename: Meixiao
authors.initials: M
authors.lastname: Long
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Adler
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D019898:Autocrine Communication; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000821:virology*; D005434:Flow Cytometry; D007376:Interleukin-2 / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D019899:Paracrine Communication; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D014616:Vaccinia virus / Q000276:immunology
chemical_list: D007376:Interleukin-2; D050799:STAT5 Transcription Factor