FLT3 Ligand Is Dispensable for the Final Stage of Type 1 Conventional Dendritic Cell Differentiation

Mechanisms of antibody mediated immunity - Distinct in early life

Immune responses in early life are characterized by a failure to robustly generate long-lasting protective responses against many common pathogens or upon vaccination. This is associated with a reduced ability to generate T-cell dependent high affinity antibodies. This review highlights the differences in T-cell dependent antibody responses observed between infants and adults, in particular focussing on the alterations in immune cell function that lead to reduced T follicular helper cell-B cell crosstalk within germinal centres in early life. Understanding the distinct functional characteristics of early life humoral immunity, and how these are regulated, will be critical in guiding age-appropriate immunological interventions in the very young.

Guidelines for mouse and human DC generation

This article is part of the Dendritic Cell Guidelines article series, which provides a collection of state-of-the-art protocols for the preparation, phenotype analysis by flow cytometry, generation, fluorescence microscopy, and functional characterization of mouse and human dendritic cells (DC) from lymphoid organs and various non-lymphoid tissues. This article provides protocols with top ticks and pitfalls for preparation and successful generation of mouse and human DC from different cellular sources, such as murine BM and HoxB8 cells, as well as human CD34+ cells from cord blood, BM, and peripheral blood or peripheral blood monocytes. We describe murine cDC1, cDC2, and pDC generation with Flt3L and the generation of BM-derived DC with GM-CSF. Protocols for human DC generation focus on CD34+ cell culture on OP9 cell layers for cDC1, cDC2, cDC3, and pDC subset generation and DC generation from peripheral blood monocytes (MoDC). Additional protocols include enrichment of murine DC subsets, CRISPR/Cas9 editing, and clinical grade human DC generation. While all protocols were written by experienced scientists who routinely use them in their work, this article was also peer-reviewed by leading experts and approved by all co-authors, making it an essential resource for basic and clinical DC immunologists.

Human dendritic cell subsets in the glioblastoma-associated microenvironment

Glioblastoma (GBM) is the most aggressive type of glioma (Grade IV). The presence of cytotoxic T lymphocyte (CTLs) has been associated with improved outcomes in patients with GBM, and it is believed that the activation of CTLs by dendritic cells may play a critical role in controlling the growth of GBM. DCs are professional antigen-presenting cells (APC) that orchestrate innate and adaptive anti-GBM immunity. DCs can subsequently differentiate into plasmacytoid DCs (pDC), conventional DC1 (cDC1), conventional (cDC2), and monocyte-derived DCs (moDC) depending on environmental exposure. The different subsets of DCs exhibit varying functional capabilities in antigen presentation and T cell activation in producing an antitumor response. In this review, we focus on recent studies describing the phenotypic and functional characteristics of DC subsets in humans and their respective antitumor immunity and immunotolerance roles in the GBM-associated microenvironment. The critical components of crosstalk between DC subsets that contribute significantly to GBM-specific immune responses are also highlighted in this review with reference to the latest literature. Since DCs could be prime targets for therapeutic intervention, it is worth summarizing the relevance of DC subsets with respect to GBM-associated immunologic tolerance and their therapeutic potential.

Murine precursors to type 1 conventional dendritic cells induce tumor cytotoxicity and exhibit activated PD-1/PD-L1 pathway

The immediate precursor to murine type 1 conventional DCs (cDC1s) has recently been established and named “pre-cDC1s”. Mature CD8α+ cDC1s are recognized for suppressing graft-versus-host disease (GvHD) while promoting graft-versus-leukemia (GvL), however pre-cDC1s have not previously been investigated in the context of alloreactivity or anti-tumor responses. Characterization of pre-cDC1s, compared to CD8α+ cDC1s, found that a lower percentage of pre-cDC1s express PD-L1, yet express greater PD-L1 by MFI and a greater percent PIR-B, a GvHD-suppressing molecule. Functional assays were performed ex vivo following in vivo depletion of CD8α+ DCs to examine whether pre-cDC1s play a redundant role in alloreactivity. Proliferation assays revealed less allogeneic T-cell proliferation in the absence of CD8α+ cDC1s, with slightly greater CD8+ T-cell proliferation. Further, in the absence of CD8α+ cDC1s, stimulated CD8+ T-cells exhibited significantly less PD-1 expression compared to CD4+ T-cells, and alloreactive T-cell death was significantly lower, driven by reduced CD4+ T-cell death. Tumor-killing assays revealed that T-cells primed with CD8α-depleted DCs ex vivo induce greater killing of A20 B-cell leukemia cells, particularly when antigen (Ag) is limited. Bulk RNA sequencing revealed distinct transcriptional programs of these DCs, with pre-cDC1s exhibiting activated PD-1/PD-L1 signaling compared to CD8α+ cDC1s. These results indicate distinct T-cell-priming capabilities of murine pre-cDC1s compared to CD8α+ cDC1s ex vivo, with potentially clinically relevant implications in suppressing GvHD while promoting GvL responses, highlighting the need for greater investigation of murine pre-cDC1s.

The correlation between Flt3-ITD mutation in dendritic cells with TIM-3 expression in acute myeloid leukemia

In general, acute myeloid leukemia (AML) is an aggressive and heterogeneous disease that is characterized by rapid cellular proliferation and high mortality. One of the mutations related to AML is the Flt3-ITD mutation, which is found in approximately 25% of patients. In this mini-review, we investigate the function of dendritic cells and T cells based on Flt3-ITD mutation and immune evasion as a result of this abnormality. Finally, we discuss some AML therapeutic strategies, including targeting Flt3 on DCs and TIM-3 on T cells as immune receptors to treat this hematopoietic malignancy.

Dendritic cell Flt3 - regulation, roles and repercussions for immunotherapy

Dendritic cells (DCs) are essential for initiating immune responses. Depending on the environment, the type of DC and the way in which they interact with T cells, these immune responses can be beneficial or detrimental. DCs can be exploited as cellular vectors for vaccines against infection and cancer. The development and maintenance of DCs is dependent on the FMS-like tyrosine kinase 3 (Flt3)/Flt3 ligand (Flt3L) signaling cascade. Flt3 is also one of the most commonly mutated genes in acute myeloid leukemia and as such represents an attractive drug target. In this review, Flt3 is discussed with a particular focus on DCs. We detail the lifecycle of Flt3, from transcription to degradation, and interrogate recent studies as to how this pathway can be manipulated for immunotherapy, vaccination and treatment of autoimmune disease.

The Collective Effect of MIP-3α and FL Promotes Dendritic Cell Function Within the Immune Microenvironment of Murine Liver Cancer

Hepatocellular carcinoma is a highly malignant and lethal tumor. In addition to surgery, immunotherapy is currently a more effective treatment for hepatocellular carcinoma. The tumor immune microenvironment (TIME) largely determines the efficacy of cancer immunotherapy. Based on the universal targeting of TIME modulators in clinical treatment, TIME modulators are promising targets for tumor immunotherapy. We investigated the effect of a double gene expression vector (recombinant galactose-terminal glycol-poly-L-lysine coupled MIP-3α-FL) on dendritic cells (DCs) regulation within the TIME of mice with liver cancer. H22 cells were transfected with a recombinant MIP-3α-FL plasmid to induce DCs differentiation and chemotaxis. The effects of transfection were investigated by flow cytometry following the modified Boyden’s method. Cytokine-induced killer (CIK) cells co-culture revealed changes in the antigen presentation ability of DCs. Further, tumor-bearing mice were injected with the recombinant double gene vector via the tail vein. We compared the survival time, tumor volume, weight of the mice, as well as the number and phenotype of tumor-infiltrating DCs (TIDCs) between groups. The supernatant of transfected H22 cells promoted the phenotypic maturation of DCs, enhancing their chemotaxis. Further, treated DCs promoted the cytokine secretion and killing ability of CIK cells. The survival time of mice injected with the double gene vector was significantly prolonged, while their tumor weight and volume were relatively reduced. Flow cytometry revealed that the number of TIDCs (as well as CD80 and CD86 expression) in the Mouse^MIP-3α-FL group, were significantly higher than in the control group. The combination of MIP-3α and FL can significantly promote DCs aggregation, maturation, and enhance their antigen presentation ability. The coupling of the double gene vector with glycosylated polylysine can improve the precise targeting of the liver and inhibit tumor growth in vivo, providing a novel approach for immune therapy in liver cancer.