Using Mice with Conditional Deletion of the IFNg Receptor to Identify the Cellular Targets of IFNg during Development of Anti-Listeria Immune Responses

Host responsiveness to IFNg is critical for resolution of Listeria infection, but the identities and roles of IFNg responsive cells that initiate this process remain unclear. In this thesis, unique mice displaying conditional loss of the IFNg receptor: Ifngr1f/f mice) in different tissues have been generated and used to explore the role of this cytokine in initiating the anti-Listeria response. Whereas Ifngr1f/f mice displayed normal cellular levels of IFNGR1 and normal resistance to Listeria infection, Vav-icre+Ifngr1f/f mice lacking IFNg responsiveness selectively in hematopoietic cells exhibited highly increased susceptibility to Listeria infection comparable to that of Ifngr1-/- mice. In contrast, Itgax-cre+ Ifngr1f/f mice lacking IFNg responsiveness selectively in dendritic cells expressing CD8a and/or CD103 displayed increased susceptibility to Listeria infection. This phenotype was traced back to a defect in the capacity of IFNg unresponsive CD8a+ DCs to produce IL-12. The IFNg required for priming CD8a+ DCs for optimal IL-12 production is derived from TNFa-activated NK/NKT cells. These mice survived Listeria infection due to a second wave of IL-12 produced by other myeloid cells. Next, Ifngr1f/f mice were bred with LysM-cre mice to obtain myeloid cell specific Ifngr1 deletion. LysM-cre+Ifngr1f/f mice lacking IFNg responsiveness selectively in both peritoneal macrophages and neutrophils succumbed to Listeria infection. Surprisingly, adoptively transferred WT neutrophils into LysM-cre+Ifngr1f/f mice seemed to completely rescue LysM-cre+Ifngr1f/f mice whereas Ifngr1-/- neutrophils did not. Thus, these results reveal that neutrophils are also one of the important targets of IFNg for Listeria resolution. This study thus demonstrates an early acting, IFNg driven cytokine and cellular cascade involving NK/NKT and CD8a+ DCs leads to rapid production of IL-12 that ultimately leads to activation of myeloid cells including macrophages and neutrophils in IFNg-rich cytokine environment

Using Mice with Conditional Deletion of the IFNg Receptor to Identify the Cellular Targets of IFNg during Development of Anti-Listeria Immune Responses

Host responsiveness to IFNg is critical for resolution of Listeria infection, but the identities and roles of IFNg responsive cells that initiate this process remain unclear. In this thesis, unique mice displaying conditional loss of the IFNg receptor: Ifngr1f/f mice) in different tissues have been generated and used to explore the role of this cytokine in initiating the anti-Listeria response. Whereas Ifngr1f/f mice displayed normal cellular levels of IFNGR1 and normal resistance to Listeria infection, Vav-icre+Ifngr1f/f mice lacking IFNg responsiveness selectively in hematopoietic cells exhibited highly increased susceptibility to Listeria infection comparable to that of Ifngr1-/- mice. In contrast, Itgax-cre+ Ifngr1f/f mice lacking IFNg responsiveness selectively in dendritic cells expressing CD8a and/or CD103 displayed increased susceptibility to Listeria infection. This phenotype was traced back to a defect in the capacity of IFNg unresponsive CD8a+ DCs to produce IL-12. The IFNg required for priming CD8a+ DCs for optimal IL-12 production is derived from TNFa-activated NK/NKT cells. These mice survived Listeria infection due to a second wave of IL-12 produced by other myeloid cells. Next, Ifngr1f/f mice were bred with LysM-cre mice to obtain myeloid cell specific Ifngr1 deletion. LysM-cre+Ifngr1f/f mice lacking IFNg responsiveness selectively in both peritoneal macrophages and neutrophils succumbed to Listeria infection. Surprisingly, adoptively transferred WT neutrophils into LysM-cre+Ifngr1f/f mice seemed to completely rescue LysM-cre+Ifngr1f/f mice whereas Ifngr1-/- neutrophils did not. Thus, these results reveal that neutrophils are also one of the important targets of IFNg for Listeria resolution. This study thus demonstrates an early acting, IFNg driven cytokine and cellular cascade involving NK/NKT and CD8a+ DCs leads to rapid production of IL-12 that ultimately leads to activation of myeloid cells including macrophages and neutrophils in IFNg-rich cytokine environment

Learning a Bayesian prior in interval timing

Behavioral studies on perceptual learning (PL) often attributed an improvement in task performance to an enhancement in sensory processing of stimuli. However, the framework of Bayesian inference suggests that perceptual improvements can arise from learning-induced changes either in a likelihood function or in a prior expectation for sensory input. We developed and adapted Bayesian observer models to long-term changes in interval timing (IT) performance by human subjects to assess relative contributions of the prior and likelihood to PL of IT.

While subjects were viewing a small bar that drifted for a while and disappeared, we estimated subjective time intervals ([DELTA]Ts) from subjects’ natural reactions to the reappearance of the invisible bar at a designated location, with the speed and distance of invisible motion varied trial to trial. Ten subjects performed this task over 10 daily sessions for [DELTA]Ts ranging from 0.5 to 6.5 sec. 

In terms of timing accuracy, the trend that short and long [DELTA]Ts were overestimated and underestimated, respectively, was evident in all subjects and became stronger over sessions. In contrast, timing precision gradually improved over session for the entire set of sampled [DELTA]Ts. These seemingly contradictory dynamics of PL in accuracy and precision were captured simultaneously by Bayesian models, in which subjective timing is determined jointly by the prior and likelihood function for IT. The best among several nested models was a simple model in which only a single Gaussian function and a single coefficient of variance were set free to describe the prior and the likelihood functions, respectively. Interestingly, it was the spread of the prior, not the likelihood, that changed steadily in the model fit to the across-session data, suggesting that the improvements in timing precision observed in our and previous studies arose as the prior became sharpened through massive training.
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Regulation of fast-spiking basket cell synapses by the chloride channel ClC-2.

Parvalbumin-expressing, fast-spiking basket cells are important for the generation of synchronous, rhythmic population activities in the hippocampus. We found that GABAA receptor-mediated synaptic inputs from murine parvalbumin-expressing basket cells were selectively modulated by the membrane voltage- and intracellular chloride-dependent chloride channel ClC-2. Our data reveal a previously unknown cell type-specific regulation of intracellular chloride homeostasis in the perisomatic region of hippocampal pyramidal neurons