Toxoplasma gondii: CD8 T Cells Cry for CD4 Help

Conclusions Toxoplasma gondii infection induces a strong innate and adaptive immune response. While the innate immunity is important for controlling the early stages of the infection (Yarovinsky, 2014), the adaptive immunity is critical for restricting the parasite replication during the later stages (Gazzinelli et al., 1992). Amongst the adaptive immune subsets, CD8 T cells are the primary effector cells while CD4 T cells play an essential helper role to maintain long-term immunity (Casciotti et al., 2002). Notwithstanding, a robust CD8 T cell immunity induced during acute phase of infection, does not result in the total eradication of parasites and the pathogen persists in a chronic state (Bhadra et al., 2011c). Studies conducted in our laboratory have shown that during chronic toxoplasmosis CD8 T cells exhibit increased expression of inhibitory receptors, especially PD-1 that leads to their dysfunction/exhaustion (Bhadra et al., 2011c). In more recent studies, we have demonstrated that CD8 T cell dysfunction is a sequelae of CD4 T cell dysfunction mediated by increased expression of the transcription factor BLIMP-1 (Hwang et al., 2016) In very recent and studies from our laboratory, we observed an increased expression of microRNA146a by antigen-specific CD4 T cells from T. gondii (Figure 1), infected animals at the time point at which elevated BLIMP-1 expression in these cells is noted. It will be very interesting and important to determine if there is a BLIMP-1/miR146a a...
Source: Frontiers in cellular and infection microbiology - Category: Microbiology Source Type: research