Protection http://www.selleckchem.com/products/Vandetanib.html mediated by IFN-��, despite elevated IL-17, suggested that IFN-�� interferes with IL-17-mediated signaling events, rather than directly influencing Th17 expression. This notion was tested by in vitro stimulation of memory CD4+ T cells derived from GKO donors in the presence of recombinant IFN-��. Exogenous IFN-�� was indeed unable to downregulate IL-17 production (Figure6C), supporting the in vivo observation that IFN-��-expressing WT CD4+ T cells did not alter CNS expression of IL-17 mRNA in WT/GKO recipients (Figure6B). The maintenance of IL-17 in the presence of IFN-�� in vitro and in vivo indicates that the phenotypes acquired during in vivo primary responses are retained in the transferred memory cells following reactivation in recipient mice.
To confirm this assumption, IFN-�� was depleted in WT/GKO recipients. WT/GKO recipients treated with anti-IFN-�� succumbed to infection by day nine p.i. similar to infected recipients of GKO CD4+ T cell (Figure6D). These data actually suggest that IFN-�� diminishes the detrimental effects of IL-17, despite the apparent expansion/survival advantage of GKO relative to WT CD4+ T cells in the infected recipients. Figure 6 IFN-��-mediated protection prevents IL-17-mediated mortality. (A) Number of CD4+ T cells in the infiltrating population and distribution of Thy1.1 positive cells measured by flow cytometry at day eight p.i. Data represent means (��SD) of … To determine potential mechanisms of IL-17-mediated mortality, IL-17-dependent chemokines and matrix metalloproteinases (MMPs) [45] were analyzed in JHMV-infected SCID recipients after transfer of WT or GKO CD4+ T cells.
Similar expression of CCL2, CCL7 and CCL20 was detected comparing infected SCID controls and GKO recipients; by contrast CCL2 and CCL7 were upregulated and CCL20 downregulated in recipients of WT CD4+ T cells (Figure7A). These data suggest that in contrast to EAE, CCL2, CCL7 and CCL20 chemokine expression is regulated by IFN-�� rather that IL-17 during JHMV infection. Moreover, no significant difference in CXCL2 mRNA was found comparing SCID-infected controls and recipients of either WT or GKO CD4+ T cells (Figure7A), supporting CXCL1 as the major neutrophil chemoattractant during JHMV infection. CNS infection with JHMV induces a limited number of MMPs, that is, MMP9, MMP3 and MMP12 [46].
As MMP9 is specifically expressed by neutrophils [47], abundant neutrophil recruitment in the CNS of GKO T cell recipients (whether or not treated with anti-IL17) correlated with MMP9 expression (Figure7B). MMP3 and MMP12 mRNA expression were also upregulated in GKO recipients compared to infected SCID controls and WT recipients, Dacomitinib suggesting a potential role of these MMPs in GKO mortality by mediating tissue destruction (Figure7B).