Calreticulin Z-IETD-FMK in vivo exposure has been shown to be of particular importance in the induction of immunogenic cell death . Exposure of calreticulin is caspase-dependent; however caspases can also mitigate the pro-inflammatory release of DAMPs from dying cells and cell death that proceeds without the activity of caspases may generate more immune-activating DAMPs [43, 56]. Such an outcome might benefit the host response. These DAMPs could escape from the cell, unimpeded by caspase-neutralisation, and proceed to work in concert with the pro-inflammatory cytokine CP-690550 solubility dmso profile we observed, to generate a better inflammatory response in the lymph node. Yet, cross-priming of T cells
is improved by caspase-dependent macrophage apoptosis [14, 57]. Whether DC death that occurs without caspase activation can elicit a CD8+ T cell response remains to be seen. It is also possible that DC death could interfere with important DC functions ATM inhibitor such as migration to local
lymph nodes for efficient antigen presentation. Others have shown that DC migration to local lymph nodes is impaired in Mtb infection [58, 59], which would delay stimulation of T cell responses. Although DC death could contribute to this phenotype, DC migration to the draining lymph node can take 18 hours in vivo after challenge with Mtb . Although we cannot extrapolate directly from our in vitro experiments to the complex environment that these cell are exposed to in vivo, infected DCs are known to traffic from the lung to lymph nodes . At low MOI, the DC may arrive at the node before undergoing
death in an environment where cell death can contribute to antigen cross-presentation. Elimination of the infected DCs could also deprive the host response of an important source of cytokines and antigen presentation; though data from Alaniz et al. suggest that DCs can serve, like macrophages, as a niche cell that promotes intracellular bacterial replication . Mtb-infected DCs produced IL-1β, IL-6, IL-8, IL-10, IL-12p70 and TNF-α as reported previously [62–66] despite the fact that the majority of the 5-FU nmr cells eventually die. The cytokine profile of Mtb-infected DCs would successfully drive differentiation of TH1 and TH17 responses . Mtb and the human immune system have co-evolved, so that one third of the global population has been colonised by this pathogen, yet the immune system is adequate at preventing disease 90% of the time [1, 2]. The central cell that regulates this host response is the dendritic cell, and consequently it is increasingly viewed as a target for new therapeutic and vaccine strategies [19, 68]. It is hoped that our description of the DC death response to Mtb infection – as pro-inflammatory, and without the activation of caspases – will inform further research that defines the T cell consequences of this innate response.