We have examined the formation, participation and functional specialization of virus-reactive Foxp3+ regulatory T cells (Tregs) in a mouse model of influenza virus infection. “Natural” Tregs generated intra-thymically based on interactions with a self-peptide proliferated in response to a homologous viral antigen in the lungs, and to a lesser extent in the lung-draining mediastinal LN (medLN), of virus-infected mice. By contrast, conventional CD4+ T cells with identical TCR specificity underwent little or no conversion to become “adaptive” Tregs. The virus-reactive Tregs in the medLN and the lungs of infected mice upregulated a variety of molecules associated with Treg activation, and also acquired expression of molecules (T-bet, Blimp-1 and IL-10) that confer functional specialization to Tregs. Notably, however, the phenotypes of the T-bet+ Tregs obtained from these sites were distinct, since Tregs isolated from the lungs expressed significantly higher levels of T-bet, Blimp-1 and IL-10 than did Tregs from the medLN. Adoptive transfer of antigen-reactive Tregs led to decreased proliferation of anti-viral CD4+ and CD8+ effector T cells in the lungs of infected hosts, while depletion of Tregs had a reciprocal effect. These studies demonstrate that thymically-generated Tregs can become activated by a pathogen-derived peptide and acquire discrete T-bet+ Treg phenotypes while participating in and modulating an antiviral immune response.
CD4+CD25+Foxp3+ regulatory T cells (Tregs) are required to restrain the immune system from mounting an autoaggressive systemic inflammatory response, but why their activity can prevent (or allow) organ-specific autoimmunity remains poorly understood. We have examined how TCR specificity contributes to Treg activity using a mouse model of spontaneous autoimmune arthritis, in which CD4+ T cells expressing a clonotypic TCR induce disease by an IL-17-dependent mechanism. Administration of polyclonal Tregs suppressed Th17 cell formation and prevented arthritis development; notably, Tregs expressing the clonotypic TCR did not. These clonotypic Tregs exerted antigen-specific suppression of effector CD4+ T cells using the clonotypic TCR in vivo, but failed to mediate bystander suppression and did not prevent Th17 cells using nonclonotypic TCRs from accumulating in joint-draining lymph nodes of arthritic mice. These studies indicate that the availability of Tregs with diverse TCR specificities can be crucial to their activity in autoimmune arthritis.
We have examined mechanisms underlying the formation of pathologic Th17 cells using a transgenic mouse model in which autoreactive CD4+ T cells recognize influenza virus hemagglutinin (HA) as a ubiquitously expressed self-antigen, and induce inflammatory arthritis. The lymph nodes of arthritic mice contain elevated numbers of inflammatory monocytes (iMO) with an enhanced capacity to promote CD4+ Th17 cell differentiation, and a regional inflammatory response develops in the paw-draining lymph nodes by an IL-17-dependent mechanism. The activation of these Th17-trophic iMO precedes arthritis development, and occurs in the context of an autoreactive CD4+ Th1 cell response. Adoptive transfer of HA-specific CD4+ T cells into non-arthritic mice expressing HA as a self-antigen similarly led to the formation of Th1 cells and of iMO that could support Th17 cell formation, and notably, the accumulation of these iMO in the lymph nodes was blocked by IFN-γ neutralization. These studies show that autoreactive CD4+ Th1 cells directed to a systemically distributed self-antigen can promote the development of a regional Th17 cell inflammatory response by driving the recruitment of Th17-trophic iMO to the lymph nodes.
A case of gongylonemiasis in a 31-year-old woman of Granada, Spain, is reported. The worm, clearly belonging to Gongylonema genus, could not be identified definitively as Gongylonema pulchrum, the species usually described in humans.
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