CCL2 has been demonstrated to have an important role in defence against L. monocytogenes infection. It is highly upregulated during the early phase of L. monocytogenes infection and attracts inflammatory monocytes, T lymphocytes, and natural killer cells to the site of microbial infection [49–51]. In the spleen, CCL2 is produced by ERTR-9+ marginal zone macrophages which are early targets of L. monocytogenes infection and

are crucial for innate immune defence [52]. High levels of CCL2, as for example induced by over expression in transgenic mice, have been demonstrated to be associated with increased sensitivity to L. monocytogenes infection [53]. Thus, elevated CCL2 levels in C3HeB/FeJ mice are likely to contribute to the overall increased detrimental inflammatory response that we have R788 concentration observed in these mice. However, this cannot explain the general host susceptibility of this mouse strain. Importantly, C3HeB/FeJ mice are susceptible to Atezolizumab many pathogens including Mycobacterium tuberculosis[54], Salmonella Typhimurium [55, 56], Plasmodium chabaudi[57], Trypanosoma rhodesiense[58], Listeria monocytogenes[59], and Streptococcus pyogenes[60, 61]. Susceptibility to M. tuberculosis and L. monocytogenes infection

in C3HeB/FeJ mice correlates with induction of severe necrotic lesions in the lung or liver and spleen, respectively [54, 59]. The multifocal abscess formation in both mouse infection models is controlled by the sst1 (supersusceptibility to tuberculosis) locus on mouse chromosome 1. Sst1 encodes the Sp110/Ipr1 nuclear body protein which belongs to the SP100/SP140 family of nuclear body proteins [54, 62]. The type I and II interferon inducible Sp110/Ipr1 gene is not expressed in C3HeB/FeJ mice due to a complex structural rearrangement at the Sst1 locus which left incomplete

copies of the Sp110/Ipr1 gene in this mouse strain [54, 62]. Consequently, mice which carry the Sst1 susceptibility allele are impaired in their innate immune response against intracellular pathogens such as M. tuberculosis and L. monocytogenes. Another host factor which greatly influences susceptibility to L. monocytogenes infection is Adenylyl cyclase the amount of interferon-β produced in response to infection [20, 21, 23, 28, 31, 32]. Production of interferon-β induces further release of type I interferons via autocrine and paracrine loops which can be detrimental due to induction of apoptosis in T cells and macrophages [63]. In addition, interferon-β is a major driver of TNF-α induced lethal shock by enhancing apoptosis of enterocytes and hepatocytes which results in bowel and liver damage [31]. We have compared induction of interferon-β responses in Lmo-InlA-mur-lux and Lmo-EGD-lux infected mice by using a luciferase reporter system and BLI in vivo imaging. Although we used Infb1-reporter mice on the L.