C5aR1 Activation Drives Early IFN-gamma Production to Control ExperimentalToxoplasma gondiiInfection

Toxoplasma gondii (T. gondii) is a parasite infecting animals and humans. In intermediate hosts, such as humans or rodents, rapidly replicating tachyzoites drive vigorous innate and adaptive immune responses resulting in bradyzoites that survive within tissue cysts. Activation of the innate immune system is critical during the early phase of infection to limit pathogen growth and to instruct parasite-specific adaptive immunity. In rodents, dendritic cells (DCs) senseT. gondiithrough TLR11/12, leading to IL-12 production, which activates NK cells to produce IFN-gamma as an essential mechanism for early parasite control. Further, C3 can bind toT. gondiiresulting in limited complement activation. Here, we determined the role of C5a/C5aR1 axis activation for the early innate immune response in a mouse model of peritonealT. gondiiinfection. We found thatC5ar1(-/-)animals suffered from significantly higher weight loss, disease severity, mortality, and parasite burden in the brain than wild type control animals. Severe infection inC5ar1(-/-)mice was associated with diminished serum concentrations of IL-12, IL-27, and IFN-gamma. Importantly, the serum levels of pro-inflammatory cytokines, including IL-1 alpha, IL-6, and TNF-alpha, as well as several CXC and CC chemokines, were decreased in comparison to wt animals, whereas anti-inflammatory IL-10 was elevated. The defect in IFN-gamma production was associated with diminishedIfngmRNA expression in the spleen and the brain, reduced frequency of IFN-gamma+NK cells in the spleen, and decreasedNos2expression in the brain ofC5ar1(-/-)mice. Mechanistically, DCs from the spleen ofC5ar1(-/-)mice produced significantly less IL-12 in response to soluble tachyzoite antigen (STAg) stimulationin vivoandin vitro. Our findings suggest a model in which the C5a/C5aR1 axis promotes IL-12 induction in splenic DCs that is critical for IFN-gamma production from NK cells and subsequent iNOS expression in the brain as a critical mechanism to control acuteT. gondiiinfection

Lung emphysema and impaired macrophage elastase clearance in mucolipin 3 deficient mice

Lung emphysema and chronic bronchitis are the two most common causes of chronic obstructive pulmonary disease. Excess macrophage elastase MMP-12, which is predominantly secreted from alveolar macrophages, is known to mediate the development of lung injury and emphysema. Here, we discovered the endolysosomal cation channel mucolipin 3 (TRPML3) as a regulator of MMP-12 reuptake from broncho-alveolar fluid, driving in two independently generated Trpml3-/- mouse models enlarged lung injury, which is further exacerbated after elastase or tobacco smoke treatment. Mechanistically, using a Trpml3IRES-Cre/eR26-τGFP reporter mouse model, transcriptomics, and endolysosomal patch-clamp experiments, we show that in the lung TRPML3 is almost exclusively expressed in alveolar macrophages, where its loss leads to defects in early endosomal trafficking and endocytosis of MMP-12. Our findings suggest that TRPML3 represents a key regulator of MMP-12 clearance by alveolar macrophages and may serve as therapeutic target for emphysema and chronic obstructive pulmonary disease

Sixth Immunotherapy of Cancer conference (ITOC): advances and perspectives—a meeting report

Immunotherapy has moved to the forefront of cancer treatment, illustrated by the accelerating pace of novel therapy approvals. In this complex environment, scientists rely on cutting edge conferences to stay informed. The Immunotherapy of Cancer (ITOC) conference was established jointly with the Society of the Immunotherapy of Cancer to bring the European researchers together. In its sixth edition, the ITOC conference has recently been held in Vienna, Austria

Monitoring C5AR2 expression using a floxed tdtomato-C5AR2 knock-in mouse

The biological significance of C5a receptor [(C5aR)2/C5L2], a seven-transmembrane receptor binding C5a and C5adesArg, remains ill-defined. Specific ligation of C5aR2 inhibits C5a-induced ERK1/2 activation, strengthening the view that C5aR2 regulates C5aR1- mediated effector functions. Although C5aR2 and C5aR1 are often coexpressed, a detailed picture of C5aR2 expression in murine cells and tissues is still lacking. To close this gap, we generated a floxed tandem dye (td)Tomato-C5aR2 knock-in mouse that we used to track C5aR2 expression in tissue-residing and circulating immune cells. We found the strongest C5aR2 expression in the brain, bone marrow, and airways. All myeloid-derived cells expressed C5aR2, although with different intensities. C5aR2 expression in blood and tissue neutrophils was strong and homogeneous. Specific ligation of C5aR2 in neutrophils from tdTomato-C5aR2 mice blocked C5a-driven ERK1/2 phosphorylation, demonstrating functionality of C5aR2 in the reporter mice. In contrast to neutrophils, we found tissue-specific differences in C5aR2 expression in eosinophils, macrophages, and dendritic cell subsets. Naive and activated T cells stained negative for C5aR2, whereas B cells from different tissues homogeneously expressed C5aR2. Also, NK cell subsets in blood and spleen strongly expressed C5aR2. Activation of C5aR2 in NK cells suppressed IL-12/IL-18-induced IFN-g production. Intratracheal IL-33 challenge resulted in decreased C5aR2 expression in pulmonary eosinophils and monocytederived dendritic cells. In summary, we provide a detailed map of murine C5aR2 immune cell expression in different tissues under steady-state conditions and upon pulmonary inflammation. The C5aR2 knock-in mouse will help to reliably track and conditionally delete C5aR2 expression in experimental models of inflammation