title: CD4 T cells, lymphopenia, and IL-7 in a multistep pathway to autoimmunity.
abstract: There are many inhibitory mechanisms that function at the cellular and molecular levels to maintain tolerance. Despite this, self-reactive clones escape regulatory mechanisms and cause autoimmunity in certain circumstances. We hypothesized that the same mechanisms that permit T cells to expand during homeostatic proliferation may inadvertently promote autoimmunity under certain conditions. One major homeostatic cytokine is IL-7, and studies have linked it or its receptor to the development of multiple sclerosis and other autoimmune diseases. We show in a model of beta-islet cell self-reactivity that the transfer of activated autoreactive CD4 T cells can prime and expand endogenous autoreactive CD8 T cells in a CD28- and CD40-dependent manner through the licensing of dendritic cells. Despite this, mice do not develop diabetes. However, the provision of exogenous IL-7 or the physiological production of IL-7 associated with lymphopenia was able to profoundly promote the expansion of self-reactive clones even in the presence of regulatory T cells. Autoimmune diabetes rapidly ensued with CD4 help and the subsequent activation of CD8 T cells, which contributed to disease progression. With the advent of many biologicals targeting TNFalpha, IL-6, and IL-1 and their effective use in the treatment of autoimmune diseases, we propose that IL-7 and its receptor may be promising targets for biological agents in the treatment of autoimmunity.
authors.affiliation: The Campbell Family Institute for Breast Cancer Research, University Health Network, Toronto, ON, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Calzascia
authors.forename: Marc
authors.initials: M
authors.lastname: Pellegrini
authors.forename: Albert
authors.initials: A
authors.lastname: Lin
authors.forename: Kristine M
authors.initials: KM
authors.lastname: Garza
authors.forename: Alisha R
authors.initials: AR
authors.lastname: Elford
authors.forename: Arda
authors.initials: A
authors.lastname: Shahinian
authors.forename: Pamela S
authors.initials: PS
authors.lastname: Ohashi
authors.forename: Tak W
authors.initials: TW
authors.lastname: Mak
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015551:Autoimmunity / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000637:transplantation; D003713:Dendritic Cells / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D007150:Immunohistochemistry; D015851:Interleukin-7 / Q000276:immunology*; D008231:Lymphopenia / Q000276:immunology*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological
chemical_list: D015851:Interleukin-7