They have also been shown to preferentially expand in a wide variety of inflammatory settings (47, 48). nodes to the infected skin to induce neutrophil recruitment, proinflammatory cytokines IL-1, IL-1, and TNF, and host defense peptides. RNA-seq for and sequences in lymph nodes and skin revealed a single clonotypic expansion of the encoded complementarity-determining region 3 amino acid sequence, which could be generated by canonical nucleotide sequences of or and and but not sequences expanded. Finally, V6+ T cells were a predominant T cell subset that produced IL-17A as well as IL-22, TNF, and IFN, indicating a broad and substantial role for clonal V6+V4+ T cells in immunity against skin infections. The gram-positive extracellular bacterium causes the vast majority of skin infections in humans (1). In addition, has become increasingly resistant to antibiotics, and multidrug-resistant community-acquired methicillin-resistant (CA-MRSA) strains cause severe skin and invasive infections (e.g., cellulitis, pneumonia, bacteremia, endocarditis, osteomyelitis, and sepsis) in otherwise healthy individuals outside of hospitals, creating a serious public health concern (2, 3). If immune-based therapies are to provide an alternative to antibiotics, an increased understanding of protective immunity against skin infections is essential. This is imperative, because all prior vaccines targeting antibody-mediated phagocytosis failed in human clinical trials (4). Notably, an vaccine targeting the surface component iron surface determinant B against deep sternal wound infections and bacteremia following cardiothoracic surgery had a worse outcome, as individuals who suffered an infection were five times more likely to die if they had received the vaccine rather than placebo (5). As an alternative to antibody responses, there has been a recent focus on T cells in contributing to protective immunity against infections. In humans, a variety of T cell subsets and cytokines has been implicated in host defense against skin infections (6C9). Similarly, in mouse models, IL-17 produced by T cells and/or Th17 cells was found to be important in neutrophil recruitment and host defense against skin and bacteremia infections (10C16). However, in vaccination attempts in mouse models of skin and bacteremia infection, the IL-17Cmediated protection was thought to be mediated by Th17 cells rather than T cells (17C20). Additionally, IFN-producing CD4+ T cells (Th1 cells) were found to contribute to protection against skin infections in patients with HIV disease as well as in wound and bacteremia Rabbit polyclonal to ANKMY2 infections in mouse models (21C23). Another study found that the IFN produced by human CD8+ T cells contributed to antigen-induced immunity against (24). We previously reported that IFN and TNF protected against a recurrent skin infection in mice deficient in IL-1 (25). Finally, several studies have reported that IL-22 contributes to host defense peptide production and bacterial Deramciclane clearance of an skin infection or mucosal colonization (10, 26C28). Taken together, these findings in humans and mice suggest Deramciclane that different T cell subsets and their cytokine responses are involved in immunity against infections. However, whether a predominant T cell subset and effector cytokine responses contribute to host defense against skin infections is unclear. In particular, the studies in humans and mice suggest an important role for IL-17 responses in immunity against skin infection. Results Recruited Lymphocytes from Lymph Nodes Are Required for IL-17CMediated Host Defense. First, to determine whether the protective T cell immune response against an skin infection was mediated by T cells residing in the skin or T cells recruited from lymph nodes, an intradermal (i.d.) infection model was used (11, 25, 29C31) in which the bioluminescent CA-MRSA USA300 LAC::strain was injected intradermally into the back Deramciclane skin of mice FTY720 (administered on days ?1, 0, and 1, and every other day thereafter until day 14 postinfection), which inhibits lymphocyte egress (including all T cells) from lymph nodes (25, 32). We chose to investigate the role of IL-17A and IL-17F because they are produced by many different T cell subsets and have been implicated in a variety of mouse models of infection as being critical to host defense (10C16). For these experiments, we used an IL-17A-tdTomato/IL-17F-GFP dual-color reporter mouse strain, which is on a C57BL/6 background and produces normal levels of IL-17A and IL-17F. Before performing in vivo experiments, this reporter mouse strain was validated in vitro by culturing CD3+ T cells from skin-draining lymph nodes of IL-17A-tdTomato/IL-17F-GFP dual-color reporter mice in the presence of Th17/IL-17 polarizing conditions. We found that the expression of Deramciclane tdTomato and GFP by Th17 cells and T cells closely corresponded to the expression of endogenous IL-17A and IL-17F protein levels using specific.