Browsing by Author "Li, Qi-Jing"

CD4+ and CD8+ T cells are dichotomous lineages in adaptive immunity. While conventionally viewed as distinct fates that are fixed post-thymic development, accumulating evidence indicates that these two populations can exhibit significant lineage plasticity, particularly upon TCR-mediated activation. In this work, I define a novel murine CD4-CD8ab+ MHCII-recognizing population generated from effector CD4+ T cells. Effector CD4-CD8ab+ MHCII-recognizing T cells downregulate expression of T helper cell-associated costimulatory molecules and increase expression of cytotoxic T lymphocyte-associated cytotoxic molecules. TCRb repertoire sequencing and in vivo genetic lineage tracing in acutely-infected wild-type mice demonstrate fundamental lineage reprogramming resulting in an “ex-CD4” T cell phenotype, rather than expansion of an aberrantly-developed CD8+ MHCII-restricted population. Impairing autophagy by functional deletion of the initiating kinase Vps34 or a downstream enzyme Atg7 dramatically enhances the generation of effector CD4-CD8ab+ MHCII-recognizing T cells. These findings suggest that effector CD4+ T cells can exhibit a previously unreported degree of skewing towards the CD8+ T cell lineage, which may point towards a novel direction for vaccine design, particularly against HIV.

The intestine is the home for trillions of microbes, collectively called microbiota. The mutualism of commensal microbes benefits intestinal health. To establish mutualism, intestinal immunity must equip with mechanisms to tolerate innocent microbiota while responding to pathogens. Intestinal immunity is coordinated by specialized and complicated mononuclear phagocytes subsets. The constitution of complex mononuclear phagocytes are thought to be similar in both small intestine and colon, however, these two organs are distinct in anatomy, microbiota abundance and composition, and immunological requirement. However, whether those distinctions require organ-specific mononuclear phagocytes to exert organ-specific immunity is unknown. To address whether there are organ-specific demands, we implement a novel mononuclear phagocyte subsetting strategy in the murine intestine and found two novel colon-specific mononuclear phagocytes: a macrophage population and a Th17-inducing dendritic cell (DC) subset. Those colon-specific DCs and macrophages surprisingly both required the transcription factor IRF4 and co-expressed DC marker CD24 and macrophage marker CD14. Novel IRF4-dependent CD14+CD24+ macrophages were markedly different from conventional macrophages in the way that novel CD14+CD24+ macrophages did not express macrophage markers CX3CR1, CD64, and CD88, and surprisingly not expressed cytokine IL-10, which is known to expressed in intestinal macrophages. Furthermore, we found that novel colon-specific CD14+CD24+ mononuclear phagocytes promote Th17 immunity in the colon and showed definitive evidence of differential requirement of mononuclear phagocytes in small intestine and colon for Th17 immunity. Our research discovered the diversity of mononuclear phagocytes with organ specificity and the organ-specific requirements for Th17 immunity.

While we found the requirement of organ-specific mononuclear phagocytes for Th17 immunity, regulation of innate-like IL-17 producing gd T cells, constituting a large source of IL-17 in intestine, is not addressed. It has been widely known that effector functions of gd T cells were pre-committed in the thymus, however, emerging evidence shows that environmental cues further re-programed gd T cell effectors. In the intestine, the major environmental cues are derived from the microbiota. Nevertheless, the microbiota-dependent regulation is controversial that some reports hold that microbiota provide immune activation signals while other reports conclude the suppressive function of microbiota. It remains unknown whether the impact of microbiota on gd T cells is activated, suppressive, or binary and whether microbiota shape gd T cells immune dynamics in distinct physiological conditions. Here, we identify that microbiota concomitantly upregulate IL-17-production and expression of the inhibitory receptor programmed cell death protein (PD-1) in gd17 T cells. The requirement of microbiota to preferentially upregulate PD-1 is conserved in gd17 T cells across multiple mucosal tissues. We determined the microbiota-driven PD-1 inhibits IL-17 production by endogenous gd17 effectors. We further show that microbiota-driven PD-1 and IL-17 phenotype are dynamics, wherein both PD-1 and IL-17 are downregulated once microbiota is depleted and is concomitantly upregulated during gut inflammation. Additionally, we found subset-specific metabolic shift in gd17 T cells that elevated lipid uptake in gd17 cells in response to intestinal inflammation linking to enhanced IL-17 production.

The coordination between adaptive and innate immune responses is essential for eradicating cancer cells. Among immune cells, DCs are the most powerful cells connecting innate and adaptive immune responses. Especially, Batf3-dependent DCs subset are thought to be key to anti-tumor immunity. The anti-tumor functions of Batf3-dependent DCs have been well reported in skin cancer, however, whether these DCs have the similar anti-tumor functions in colorectal cancer is largely unknown. Here, we investigated the roles of Batf3-dependent DCs in a spontaneous colorectal cancer and surprisingly found that these DCs promoted colon tumorigenesis. We identified an unconventional function of Batf3-dependent DCs to promote tumor infiltrating gd17 T cells in colon tumor instead of expanding anti-tumor IFNg-producing T cells. Proinflammatory cytokine IL-17 is known to promote colon tumor and the pro-tumor role of gd17 T cells have been proposed in several cancers including colorectal cancer. Mechanistically, we determined that Batf3-dependent DCs promote recruitment of gd17 T cells in colon tumor but are not required for gd17 T cells survival or proliferation. As we found that microbiota drives IL-17 production in gd17 T cells, the production of tumor infiltrating endogenous effector gd17 T cells and colon tumor growth were microbiota-dependent. Our study revealed a requirement of Batf3-dependent DCs to regulate tumor infiltrating gd17 T cells and the effector function is modulated by microbiota in colon tumor.

T cells have long been regarded as essential contributors in cancer surveillance and autoimmune disease, due to their vast abilities to coordinate, execute and monitor the adaptive immune response. Although many studies have focused on the important contributions of circulating memory T cells in cancer, there is a large knowledge gap in the development and functions of the recently characterized tissue-resident memory T cell population in the tumor. In addition, while significant strides have been made in understanding the pathogenesis of certain types of cancer, other types are less well understood. In this dissertation, I seek to understand the roles that tissue-resident memory T cells play in cancer by using high-throughput technologies to understand the clonal relationship of T cells in different tissues and to elucidate their tumor protective mechanisms at the single cell level. In a less characterized model of glioma, I also seek to expand our knowledge of the role of circulating effector T cells and to apply these findings to cancer immunotherapy with a novel form of adoptive T cell transfer.Tissue resident memory T cells (TRMs) develop after initial virus encounter and rapidly clear the pathogen. In the tumor environment, the association between increased TRMs in the tumor and prolonged patient survival has been well documented; however, TRM development and direct functions in tumorigenesis remain elusive. To address this, we used a murine breast cancer model and tracked TRM development in the tumor and in the contralateral distant mammary mucosa tissue. Single-cell RNA-sequencing of both intratumor and distant mucosa TRMs revealed two phenotypically distinct populations of TRMs representing their active and quiescent state. We found that TRMs in different tissue compartments shared the same TCR clonotypes and transcriptomes with a subset of intratumoral effector/effector memory T cells (TEff/EMs), clarifying their developmental ontogeny. At the mechanistic level, we showed that tumor production of CXCL16 maintains CXCR6+ TEff/EMs in the tumor, while the CXCR6- population egressed the tumor to form distant TRMs. We found that releasing CXCR6 mediated retention in the primary tumor led to superior control against lung metastases, indicating a potential direct role of TRMs in protection against tumor metastasis. Furthering our understanding of the circulating T cell response in gliomagenesis, we focused on mutant IDH1 gliomas. Despite the presence of this mutation in most low grade gliomas, there are still many remaining questions about the immune landscape during tumor formation and a lack of therapeutic targets. Using novel compound genetic mouse models that recapitulate the hallmark features of mutant IDH1 glioma, we performed high throughput TCR repertoire sequencing in mutant IDH1 versus WT IDH1 gliomas. Surprisingly, the glioma genotypes showed little differences in T cell infiltration and expansion. Extensive in vitro profiling experiments confirmed this, showing that the metabolite produced by mutant IDH1 tumors, D-2HG, had little effect on the skewing of the immune response. We developed an engineered T Cell Receptor (TCR-T) adoptive cell transfer based approach to identify and clone mutant IDH1 expressing T cells. We hope this collection of T cells will be useful in the immunotherapy of gliomas. Finally, we synthesized and biologically evaluated novel immune-suppressive therapies for the treatment of autoimmune diseases. While treatment options for autoimmune diseases have increased over the past several years, they are limited in their clinical efficacy by high drug toxicity and lack of selectivity. Thus, we sought new immunomodulatory agents with lower toxicity. Our previous work identified subglutinol A as a natural agent that exerts immune-suppressive effects on activated T cells. To provide guiding principles in future therapeutic development and to specifically define the structural requirements of subglutinols that exert their immunomodulatory activity, we prepared and evaluated the immunomodulatory activities of several subglutinol analogs. Though in vitro studies of structure-activity relationship, we identified a new subglutinol analog with reduced structural complexity. It will serve as a potential lead compound for future autoimmune drug development. This new subglutinol A compound, when compared to its parent compound, effectively suppressed inflammatory IFN and IL-17A cytokine production and has reduced T cell toxicity. Using a mouse model of experimental autoimmune encephalitis (EAE), we found that in vivo treatment of this new analog did not ameliorate the symptoms of disease, although it significantly increased the percentage of inflammatory neutrophils. These results suggest that, while not effective in EAE, this compound has potential as a novel therapy in diseases where promoting an influx of inflammatory neutrophils is beneficial.