No abstract

Natural killer (NK) cells have been reported to control adaptive immune responses that occur in lymphoid organs at the early stages of immune challenge. The physiological purpose of such regulatory activity remains unclear, because it generally does not confer a survival advantage. We found that NK cells specifically eliminated activated CD4(+) T cells in the salivary gland during chronic murine cytomegalovirus (MCMV) infection. This was dependent on TNF-related apoptosis inducing ligand (TRAIL) expression by NK cells. Although NK cell-mediated deletion of CD4(+) T cells prolonged the chronicity of infection, it also constrained viral-induced autoimmunity. In the absence of this activity, chronic infection was associated with a Sjogren's-like syndrome characterized by focal lymphocytic infiltration into the glands, production of autoantibodies, and reduced saliva and tear secretion. Thus, NK cells are an important homeostatic control that balances the efficacy of adaptive immune responses with the risk of developing autoimmunity.

Integrative Physiology B lood vessels consist of 2 major cell types, endothelial and mural cells, such as pericytes and vascular smooth muscle cells (VSMC), which surround the endothelium. Regulator of G-protein signaling 5 (RGS5) is expressed in mural cells and has emerged as a crucial modulator of vascular pathology in cancer. For instance, we have demonstrated that RGS5 is highly upregulated in angiogenic tumor pericytes.1 Loss of RGS5 results in pericyte maturation and normalization of tumor vasculature.2,3 Moreover, we showed a crucial role for RGS5 in regulating vascular barrier function in tumors and in brain capillaries during ischemia, and also provided the first genetic evidence that RGS5 is involved in vascular wall remodeling in adults. 2A striking feature of RGS5 expression is its dynamic nature in various physiological and pathological states, which indicates a role in adaptive processes. 1,[4][5][6] This is consistent with RGS5 being a member of the extended family of RGS molecules, which are modulators of G-protein-coupled receptors (GPCRs). G-protein signaling pathways rely on rapid on-off kinetics, and RGS molecules act as GTPaseactivating proteins (GAP) for heterotrimeric G proteins and, as such, regulate duration and intensity of signaling events. They contain a highly conserved carboxyl-terminal RGS domain that confers the catalytic function for active Gα subunits. Members of the R4/B subfamily, which include, among others, RGS 2, 4, and 5, are the smallest RGS Original received September 21, 2012; revision received January 7, 2013; accepted January 9, 2013. In December 2012, the average time from submission to first decision for all original research papers submitted to Circulation Research was 14.5 days.