Characterization of Thymic Development of Natural Killer T Cell Subsets by Multiparameter Flow Cytometry

RORγt agonist enhances anti-PD-1 therapy by promoting monocyte-derived dendritic cells through CXCL10 in cancers

Background

The overall response rate to checkpoint blockade remains unsatisfactory, partially due to the immune-suppressive tumor microenvironment. A retinoic acid-related orphan receptor γt (RORγt) agonist (LYC-55716) is currently used in clinical trials combined with anti-PD-1, but how the Th17 cell transcription factor RORγt enhances antitumor immunity of PD-1 in the tumor microenvironment remains elusive.

Methods

The expression of mRNA was analyzed using qPCR assays. Flow cytometry was used to sort and profile cells. Cell migration was analyzed using Transwell assays. Biacore was used to determine the binding affinity to the RORγt protein. The RORγt GAL4 cell-based reporter gene assay was used to measure activity in the RORγt driven luciferase reporter gene expression.

Results

We designed a potent and selective small-molecule RORγt agonist (8-074) that shows robust antitumor efficacy in syngeneic tumor models and improves the efficacy of anti‑PD‑1 in a murine lung cancer model. RORγt agonist treatment increased intratumoral CD8+ T cells, which were correlated with CXCL10 and monocyte-derived dendritic cells (MoDCs). In addition, the RORγt agonist promoted Type 17 T cell migration by upregulating CCL20 and CCR6 expression, and Type 17 T cell tumor infiltration. CCL20 induces MoDCs migration, and CXCL10 derived from MoDCs promotes CD8+ T cell migration.

Conclusion

Our results revealed that the RORγt agonist improved the efficacy of anti-PD-1. The RORγt agonist increased the migration of MoDCs, which increased the local levels of CXCL10, thus promoting CD8+ T cell tumor infiltration. Our findings provide the mechanistic insights implicating the RORγt agonist in immunotherapy and offer a strategy for targeting the RORγt agonist to improve PD-1 antibody efficacy in cancers.

Isolation and Detection of Murine iNKT Cells in Different Organs

The invariant NKT (iNKT) cells are innate-like lymphocytes that share phenotypic and functional characteristics with NK cells and T cells, playing an important role in both human and mouse physiology and disease and bridging the gap between the innate and adaptive immune responses. The frequency and subtypes of iNKT cells in major immune organs are different, which also determines the regional immune characteristics of iNKT cells. Here, we report a protocol about the isolation of iNKT cells in the thymus, spleen, and liver of C57BL/6, CD1d^-/-, and Jα18^-/- mice.

Identification of Rare Thymic NKT Cell Precursors by Multiparameter Flow Cytometry

Mouse invariant natural killer T (NKT) cells are a subset of T lymphocytes which have been shown to play a significant role in innate and adaptive immune responses. Features of innate responses are attributed to these cells because they can be stimulated simultaneously with the same ligand to produce quickly and in large amount cytokines without prior immunization. Because these characteristics could be exploited for clinical applications, NKT cells have attracted considerable interest. Many studies have investigated the molecular mechanisms through which they are selected and differentiate. These studies are based on developmental models that serve as a scaffold to understand the specific roles played by various factors and to identify checkpoints during cellular development. Analysis of NKT cell precursors at the HSA^high stage, stage 0, can reveal potential selection defects, whereas analysis of NKT cells at the HSA^low stage can shed light on defects in the maturation/differentiation of the different NKT cell subsets (NKT1, 2, and 17). Unlike HSA^low NKT cell subsets, HSA^high NKT cell precursors are not accurately identified by flow cytometry because of their extreme rarity. Here, we describe an NKT cell enrichment strategy to identify unambiguously NKT cell precursors at the HSA^high stage that can be used to assess their distribution and characteristics by multicolor flow cytometry.

Zeb1 represses TCR signaling, promotes the proliferation of T cell progenitors and is essential for NK1.1+ T cell development

T cell development proceeds under the influence of a network of transcription factors (TFs). The precise role of Zeb1, a member of this network, remains unclear. Here, we report that Zeb1 expression is induced early during T cell development in CD4-CD8- double-negative (DN) stage 2 (DN2). Zeb1 expression was further increased in the CD4+CD8+ double-positive (DP) stage before decreasing in more mature T cell subsets. We performed an exhaustive characterization of T cells in Cellophane mice that bear Zeb1 hypomorphic mutations. The Zeb1 mutation profoundly affected all thymic subsets, especially DN2 and DP cells. Zeb1 promoted the survival and proliferation of both cell populations in a cell-intrinsic manner. In the periphery of Cellophane mice, the number of conventional T cells was near normal, but invariant NKT cells, NK1.1+ γδ T cells and Ly49+ CD8 T cells were virtually absent. This suggested that Zeb1 regulates the development of unconventional T cell types from DP progenitors. A transcriptomic analysis of WT and Cellophane DP cells revealed that Zeb1 regulated the expression of multiple genes involved in the cell cycle and TCR signaling, which possibly occurred in cooperation with Tcf1 and Heb. Indeed, Cellophane DP cells displayed stronger signaling than WT DP cells upon TCR engagement in terms of the calcium response, phosphorylation events, and expression of early genes. Thus, Zeb1 is a key regulator of the cell cycle and TCR signaling during thymic T cell development. We propose that thymocyte selection is perturbed in Zeb1-mutated mice in a way that does not allow the survival of unconventional T cell subsets.

Transnuclear mice reveal Peyer's patch iNKT cells that regulate B-cell class switching to IgG1

Tissue-resident iNKT cells maintain tissue homeostasis and peripheral surveillance against pathogens; however, studying these cells is challenging due to their low abundance and poor recovery from tissues. We here show that iNKT transnuclear mice, generated by somatic cell nuclear transfer, have increased tissue resident iNKT cells. We examined expression of PLZF, T-bet, and RORγt, as well as cytokine/chemokine profiles, and found that both monoclonal and polyclonal iNKT cells differentiated into functional subsets that faithfully replicated those seen in wild-type mice. We detected iNKT cells from tissues in which they are rare, including adipose, lung, skin-draining lymph nodes, and a previously undescribed population in Peyer's patches (PP). PP-NKT cells produce the majority of the IL-4 in Peyer's patches and provide indirect help for B-cell class switching to IgG1 in both transnuclear and wild-type mice. Oral vaccination with α-galactosylceramide shows enhanced fecal IgG1 titers in iNKT cell-sufficient mice. Transcriptional profiling reveals a unique signature of PP-NKT cells, characterized by tissue residency. We thus define PP-NKT as potentially important for surveillance for mucosal pathogens.