This study investigated the unresolved issue of antigen-dependency and antigen-specificity of autoimmune disease suppression by CD4+CD25+ T cells (T regs). Based on autoimmune ovarian disease (AOD) in day 3 thymectomized (d3tx) mice and polyclonal T regs expressing the Thy1.1 marker, we determined: (a) the location of recipient T cell suppression, (b) the distribution of AOD-suppressing T regs, and (c) the relative efficacy of male versus female T regs. Expansion of recipient CD4+ T cells, activation/memory marker expression, and IFN-gamma production were inhibited persistently in the ovary-draining LNs but not elsewhere. The cellular changes were reversed upon Thy1.1+ T reg depletion, with emergence of potent pathogenic T cells and severe AOD. Similar changes were detected in the regional LNs during autoimmune dacryoadenitis and autoimmune prostatitis suppression. Although the infused Thy1.1+ T regs proliferated and were disseminated in peripheral lymphoid organs, only those retrieved from ovary-draining LNs adoptively suppressed AOD at a suboptimal cell dose. By depriving d3tx recipients of ovarian antigens, we unmasked the supremacy of ovarian antigen-exposed female over male T regs in AOD suppression. Thus, disease suppression by polyclonal T regs depends on endogenous antigen stimulation; this occurs in a location where potent antigen-specific T regs accumulate and continuously negate pathogenic T cell response.
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"CD4 + CD25 + Treg cells have a potential to avert differentiation of autoimmune effector T cells from the peripheral pool of memory cells and therefore prevent disease development . Antigen-dependent polyclonal CD4 + CD25 + Treg cells, in the regional lymph nodes serve a function of continuously regulating autoimmune responses throughout the course of the dis- ease  . Mechanisms of Treg cell-mediated immunological tolerance in MS have been critically reevaluated . "
"Although the limited understanding of Treg cell specificity has precluded a comprehensive test of this possibility in vivo, it is interesting to note that only Treg cells from male mice can effectively ameliorate autoimmune prostatitis caused by Treg cell depletion due to neonatal thymectomy (144). Conversely, autoimmune oophoritis is most effectively controlled by Treg cells from female mice, particularly those isolated from the tissue-draining lymph nodes (145). Thus, despite the fact that both male and female Treg cells presumably contain specificities for shared and ubiquitously expressed self-antigens present in the prostate and ovaries, these were not sufficient to prevent disease development, indicating a tremendous degree of antigen specificity in these regulatory responses. "
[Show abstract][Hide abstract]ABSTRACT: Foxp3(+) regulatory T cells (Treg cells) are essential for establishing and maintaining self-tolerance, and also inhibit immune responses to innocuous environmental antigens. Imbalances and dysfunction in Treg cells lead to a variety of immune-mediated diseases, as deficits in Treg cell function contribute to the development autoimmune disease and pathological tissue damage, whereas overabundance of Treg cells can promote chronic infection and tumorigenesis. Recent studies have highlighted the fact that Treg cells themselves are a diverse collection of phenotypically and functionally specialized populations, with distinct developmental origins, antigen-specificities, tissue-tropisms, and homeostatic requirements. The signals directing the differentiation of these populations, their specificities and the mechanisms by which they combine to promote organ-specific and systemic tolerance, and how they embody the emerging property of regulatory memory are the focus of this review.
Full-text · Article · Jul 2014 · Frontiers in Immunology
"These results suggest that in this experimental setting, the two different immune outcomes (graft protection or damage) are probably not caused by a difference in the numbers of T eff cells expanded during the priming phase. Alternatively, the results highlighted the critical requirement of sufficient recruitment of T reg cells to the inflammatory site and the continuous presence of T reg cells for optimal suppression , as suggested in previous studies with models of autoimmune oophoritis (Samy et al., 2005), islet transplantation (Zhang et al., 2009), and other models of immune-mediated (Tisch and Wang, 2008; Shevach, 2011). To further examine the behavior of T reg cells in a setting of severe imbalance with T eff cells, we examined the impact of acute removal of T reg cells after establishment of target tissue protection. "
[Show abstract][Hide abstract]ABSTRACT: Real-time imaging studies are reshaping immunological paradigms, but a visual framework is lacking for self-antigen-specific T cells at the effector phase in target tissues. To address this issue, we conducted intravital, longitudinal imaging analyses of cellular behavior in nonlymphoid target tissues to illustrate some key aspects of T cell biology. We used mouse models of T cell-mediated damage and protection of pancreatic islet grafts. Both CD4(+) and CD8(+) effector T (Teff) lymphocytes directly engaged target cells. Strikingly, juxtaposed β cells lacking specific antigens were not subject to bystander destruction but grew substantially in days, likely by replication. In target tissue, Foxp3(+) regulatory T (Treg) cells persistently contacted Teff cells with or without involvement of CD11c(+) dendritic cells, an observation conciliating with the in vitro "trademark" of Treg function, contact-dependent suppression. This study illustrates tolerance induction by contact-based immune cell interaction in target tissues and highlights potentials of tissue regeneration under antigenic incognito in inflammatory settings.
Full-text · Article · Feb 2014 · Journal of Experimental Medicine