IL6 and infection: Experimental evidence evaluating the induction of PD-1 and PDL-1 after infection with TMEV in normal and transgenic IL-6 mice showed that the excessive production of IL-6 displayed by transgenic mice after infection positively correlates with increased up-regulation of PD-1 and PDL-1 molecules in the central nervous system, and consequently with reduced CD8+ cytolytic function (Jin et al., 2013).