Plasmacytoid dendritic cells (pDCs) are specialized immune cells best known for their ability to produce large amounts of type I interferons (IFN-I) upon nucleic acid sensing through endosomal Toll-like receptors (TLR)-7/8 and 9. In tumors, the accumulation of nucleic acids (NAs) deriving from extensive cancer cell death would be expected to activate pDCs and induce IFN-I–mediated anti-tumor responses. However, tumor-infiltrating pDCs typically exhibit impaired IFN-I production and instead acquire immunosuppressive properties, revealing a paradox between NAs availability and pDC function within the tumor microenvironment (TME). In this review, we examine current knowledge and explore the mechanisms that may constrain IFN-I responses by pDCs, including chronic stimulation, alterations in TLR signaling and limited accessibility of tumor-derived NAs. We discuss key open questions regarding how tumor-associated signals may impair pDC responsiveness and contribute to their dysfunction, the nature and immunostimulatory potential of tumor-derived NAs, and their intracellular delivery. By highlighting these unresolved questions, we propose conceptual frameworks to better understand pDC biology in cancer and identify strategies to restore their IFN-I–mediated antitumor functions.

IntroductionImmunity in the vaginal mucosa (VM) is of critical importance for the protection from infections and cancers. Dendritic cells (DCs) are the major antigen-presenting cells that can induce and control T cell responses. Interestingly, VM Langerhans cells (vLCs) and VM CD1c+CD14- DCs (vDCs) polarize CD4+ T cells toward Th2-type. However, the mechanisms underlying Th2 polarization by vDCs remain unknown.MethodsOX40L expression was determined in the human VM tissue sections, followed by the measurement of OX40L expression on vLCs, CD1c+CD14- vDCs, and VM macrophages (vMØs) by flow cytometry. The roles of OX40L on vDC subsets in the induction of different types of CD4+ T cell responses were assessed.ResultsBoth vLCs and CD1c+CD14- vDCs express surface OX40L. Neutralizing OX40L with anti-OX40L antibody significantly decreased the frequency of Th2-type CD4+ T cells with a reduction of CD4+ T cell proliferation, while increasing the frequency of IL - 10-producing CD4+ T cell responses. Anti-OX40L did not affect vLC- or CD1c+CD14- vDC-induced Th1-type T cell responses. OX40L also contributed to the induction of IL - 21+CD4+ T cell responses by vLCs and CD1c+CD14- vDCs. In contrast to vLCs and CD1c+CD14- vDCs, vMØs expressed a minimal level of surface OX40L. Likewise, anti-OX40L did not significantly affect vMØ-induced CD4+ T cell responses.ConclusionsOX40L contributes to vLC- and CD1c+CD14- vDC-induced Th2 polarization. It also significantly affects the frequency of vLC- and CD1c+CD14- vDC-induced IL - 10+ and IL - 21+CD4+ T cells. This study provides new insights into the immunological landscape of the human VM tissues, with implications for the development of targeted immunomodulatory strategies at this mucosal site.

We induced systemic sclerosis (SSc)-like disease in both wild-type and Dnase1l3-deficient mice using two distinct approaches involving bleomycin and hypochlorous acid injections. Our observations revealed that the deficiency in DNASE1L3 did not affect tissue fibrosis or inflammation caused by these treatments. Despite the association of single nucleotide polymorphisms in humans with SSc pathogenesis, our study demonstrates that DNASE1L3 is dispensable in two inducible murine models of SSc-like pathogenesis.

Chronic histiocytic intervillositis of unknown origin (CHI) is a rare placental disorder associated with adverse pregnancy outcomes, frequent recurrence, and a lack of effective preventive strategies. Recent insights indicate a potential link between CHI-associated inflammatory lesions and the inflammasome pathway, suggesting innovative therapeutic avenues. This study aims to elucidate the role of the inflammasome pathway in CHI through comprehensive transcriptomic analysis of grade 2 or 3 histopathologic CHI samples, paired with placental controls. Additionally, we present case studies of three individuals with recurrent CHI who received treatment with anakinra and colchicine throughout pregnancy, resulting in improved perinatal outcomes. Notably, all cases led to the birth of healthy, full-term infants, with reduced or absent intervillositis recurrence. Placental assessment unveiled heightened activation of the NLRP3-PYCARD inflammasome pathway and IL-1β processing in CHI samples, with downregulation observed in treated pregnancy samples devoid of intervillositis. Collectively, these findings suggest a potential therapeutic role for targeting the inflammasome pathway in preventing recurrent CHI in pregnant individuals. The molecular insights provided herein open doors for innovative interventions in managing this rare placental disorder, warranting further investigation and consideration.

Dendritic cells are cells of hematopoietic origin that are specialized in antigen presentation and instruction of innate and adaptive immune responses. They are a heterogenous group of cells populating lymphoid organs and most tissues. Dendritic cells are commonly separated in three main subsets that differ in their developmental paths, phenotype, and functions. Most studies on dendritic cells were done primarily in mice; therefore, in this chapter, we propose to summarize the current knowledge and recent progress on mouse dendritic cell subsets' development, phenotype, and functions.

Supplementary Materials and Methods: This section includes additional Materials and Methods. Supplementary Figure S1: Specificity and binding ability of αCD40 (12E12) antibody. Supplementary Figure S2. αCD40-HPV16.E6/7 can target CD40 and can thus bind to human DCs and B cells. Supplementary Figure S3. αCD40-HPV16.E6/7 can induce E6/7-specific CD8+ and CD4+ T cell responses in vivo. Supplementary Figure S4. Poly(I:C) effectively enhances antigen-specific CD8+ T cell response in human in vitro. Supplementary Figure S5. Poly(I:C) effectively enhances antigen-specific CD8+ T cell response in CD40Tg mice in vivo.

Chronic lymphocytic leukemia (CLL) is characterized by an expansion of mature B cells in the bone marrow, peripheral lymphoid organs, and blood. CD4 T helper (Th) lymphocytes significantly contribute to the physiopathology of CLL, but the subset(s) of Th cell involved in CLL pathogenesis is (are) still under debate. In this study, we performed flow cytometry analysis of the circulatory T cells of untreated CLL patients and observed an increase in follicular helper T cells (Tfh), which is a subset of T cells specialized in B cell help. Elevated numbers of Tfh cells correlated with disease severity as measured by the Binet staging system. Tfh from CLL patients were activated and skewed toward a Th1 profile as evidenced by their PD-1+IL-21+IFNγ+ phenotype and their CXCR3+CCR6- chemokine receptor profile. Tfh efficiently enhanced B-CLL survival and proliferation through IL-21 but independently of IFNγ. Finally, we observed an inverse correlation between the Tfh1 and IgA and IgG serum levels in patients, suggesting a role for this Tfh subset in the immune dysfunction associated with CLL. Altogether, our data highlight an impairment in circulatory Tfh subsets in CLL patients and their critical role in CLL physiopathology.

All supplementary Figures S1-S5. FIGURE S1. Gating scheme. FIGURE S2. Effect of chemoradiation on circulating immunocytes. FIGURE S3. Intracellular IFN-γ and TNF-α staining in CD8+ and CD4+ T cells. FIGURE S4. Effect of chemoradiotherapy on PD-1 expression on CD8+T cells. FIGURE S5. Baseline PD-1 expression is correlated with post-treatment PD-1 expression on CD4+ T cells.

Supplementary Table 1. Absolute Numbers for immune population

Dendritic cells (DCs) are antigen-presenting cells (APCs) that shape innate and adaptive immunity. There are multiple subsets of DCs distinguished according to their phenotype and functional specialization. DCs are present in lymphoid organs and across multiple tissues. However, their frequency and numbers at these sites are very low making their functional study difficult. Multiple protocols have been developed to generate DCs in vitro from bone marrow progenitors, but they do not fully recapitulate DC complexity found in vivo. Therefore, directly amplifying endogenous DCs in vivo appears as an option to overcome this specific caveat. In this chapter, we describe a protocol to amplify murine DCs in vivo by the injection of a B16 melanoma cell line expressing the trophic factor FMS-like tyrosine kinase 3 ligand (Flt3L). We have also compared two methods of magnetic sorting of amplified DCs, both giving high yields of total murine DCs, but different representation of the main DC subsets found in vivo.

Supplementary figure legends

Nuclear hormone receptors (NHRs) expressed by dendritic cells (DCs), the major immune inducers and regulators, could play important roles in host immunity. Assessment of NHRs expressed by DCs in the vaginal mucosa (VM), in comparison with those expressed by DCs in other tissues, will thus help us understand the immunology of human vagina. This study identified 16 NHR transcripts that are differentially expressed among 8 different antigen-presenting cell (APC) subsets isolated from human VM, skin, and blood. The expression profiles of NHRs were largely tissue specific. VM APCs expressed increased levels of LXRA, RXRA, ESRRA, ESRRAP2, and PPARG, whereas skin and blood APCs expressed increased levels of NURR1, NOR1 and RARA. Of interest, female sex hormone receptors, ESR1 and PGR, were found to be mainly expressed by non-APC cell types in the VM; ESR1 by HLA-DR+CD34+ and PGR by HLA-DR- cells. ERα and PR were expressed by vimentin+ cells in the VM, but not in human skin. ERα, but not PR, was also expressed in CD10+ cells in the lamina propria of VM. In conclusion, NHR expression by APC subsets is tissue- and cell type-specific. Future studies on the roles of individual NHRs expressed by different cell types, including DC subsets, in the human VM are warranted.

OBJECTIVE:To characterize the role of interleukin-1β (IL-1β) and microvascular endothelial cells (MVECs) in the generation of alternatively activated macrophages in the skin, and to explore their role in the development of skin fibrosis in patients with systemic sclerosis (SSc; scleroderma).METHODS:Conditioned medium prepared with MVECs purified from the skin of healthy donors and the skin of SSc patients was used to generate monocyte-derived macrophages. Flow cytometry, multiplex protein assessment, real-time quantitative polymerase chain reaction, and tissue immunofluorescence were used to characterize MVEC-induced polarization of alternatively activated macrophages. Coculture experiments were conducted to assess the role of MVEC-induced alternatively activated macrophages in fibroblast activation. Alternatively activated macrophages were characterized in the skin of healthy donors and SSc patients using multiparametric immunofluorescence and multiplex immunostaining for gene expression. Based on our in vitro data, we defined a supervised macrophage gene signature score to assess correlation between the macrophage score and clinical features in patients with SSc, using the Spearman's test.RESULTS:IL-1β-activated MVECs from SSc patients induced monocytes to differentiate into DC-SIGN+ alternatively activated macrophages producing high levels of CCL18, CCL2, and CXCL8 but low levels of IL-10. DC-SIGN+ alternatively activated macrophages showed significant enhancing effects in promoting the production of proinflammatory fibroblasts and were found to be enriched in perivascular regions of the skin of SSc patients who had a high fibrosis severity score. A novel skin transcriptomic macrophage signature, defined from our in vitro findings, correlated with the extent of skin fibrosis (Spearman's r = 0.6, P = 0.0018) and was associated with early disease manifestations and lung involvement in patients with SSc.CONCLUSION:Our findings shed new light on the vicious circle implicating unabated IL-1β secretion, MVEC activation, and the generation of DC-SIGN+ alternatively activated macrophages in the development of skin fibrosis in patients with SSc.

Female sex hormones affect the immune response in the lower female genital tract. To understand their mechanisms of action, it is essential to define cell types expressing estrogen receptor (ER) and/or progesterone receptor (PR) in the human vaginal mucosa (VM). Here, we report that none of the dendritic cell (DC) subsets in the human VM expressed ERα or PR in situ. However, they were capable of expressing ERα, but not PR, after in vitro culture of the whole VM tissues. Similarly, ERα and/or PR expression by T cells in the VM tissues was also inducible rather than constitutive. In contrast, ERα and/or PR were constitutively expressed in HLA-DR- non-immune cell types (vimentin+, desmin+, or CD10+). These new findings will help us understand the mechanisms of action of female sex hormones in the modulation of immune response in the human VM and lower female genital tract.

Common variable immunodeficiency is the most common clinical primary immunodeficiency in adults. Its hallmarks are hypogammaglobulinemia and compromised B-cell differentiation into memory or antibody-secreting cells leading to recurrent infections. This disease is heterogeneous, with some patients harboring multiple complications such as lymphoproliferative disorders, autoimmune manifestations or granulomatous inflammation. The mechanisms leading to these complications remain elusive despite numerous associations found in the literature. For instance, although described as a B cell intrinsic disease, numerous abnormalities have been reported in other immune cell compartments. Here, we tuned our attention to follicular helper T cells, a CD4+ T cell population specialized in B cell help, considering the recent publications showing an involvement of these cells in CVID pathogenesis.

In contrast to the once dominant tumour‐centric view of cancer, increasing attention is now being paid to the tumour microenvironment (TME), generally understood as the elements spatially located in the vicinity of the tumour. Thinking in terms of TME has proven extremely useful, in particular because it has helped identify and comprehend the role of nongenetic and noncell‐intrinsic factors in cancer development. Yet some current approaches have led to a TME‐centric view, which is no less problematic than the former tumour‐centric vision of cancer, insofar as it tends to overlook the role of components located beyond the TME, in the ‘tumour organismal environment’ (TOE). In this minireview, we highlight the explanatory and therapeutic shortcomings of the TME‐centric view and insist on the crucial importance of the TOE in cancer progression.

T follicular helper (Tfh) cells are a distinct subset of CD4+ T lymphocytes, specialized in B cell help and in regulation of antibody responses. They are required for the generation of germinal center reactions, where selection of high affinity antibody producing B cells and development of memory B cells occur. Owing to the fundamental role of Tfh cells in adaptive immunity, the stringent control of their production and function is critically important, both for the induction of an optimal humoral response against thymus-dependent antigens but also for the prevention of self-reactivity. Indeed, deregulation of Tfh activities can contribute to a pathogenic autoantibody production and can play an important role in the promotion of autoimmune diseases. In the present review, we briefly introduce the molecular factors involved in Tfh cell formation in the context of a normal immune response, as well as markers associated with their identification (transcription factor, surface marker expression, and cytokine production). We then consider in detail the role of Tfh cells in the pathogenesis of a broad range of autoimmune diseases, with a special focus on systemic lupus erythematosus and rheumatoid arthritis, as well as on the other autoimmune/inflammatory disorders. We summarize the observed alterations in Tfh numbers, activation state, and circulating subset distribution during autoimmune and some other inflammatory disorders. In addition, central role of interleukin-21, major cytokine produced by Tfh cells, is discussed, as well as the involvement of follicular regulatory T cells, which share characteristics with both Tfh and regulatory T cells.

The notion of tumor microenvironment (TME) has been brought to the forefront of recent scientific literature on cancer. However, there is no consensus on how to define and spatially delineate the TME. We propose that the time is ripe to go beyond an all-encompassing list of the components of the TME, and to construct a multilayered view of cancer. We distinguish six layers of environmental interactions with the tumor and show that they are associated with distinct mechanisms, and ultimately with distinct therapeutic approaches.

Common variable immunodeficiency (CVID) is characterized by low levels of circulating immunoglobulins and defects in B cell maturation leading to an increased susceptibility to infections. Some patients develop complications such as autoimmune diseases, enteropathy, and lymphoproliferation, resulting in higher morbidity and mortality. Follicular helper T (Tfh) cells are specialized in helping B cell differentiation into Ig-producing cells. Three subsets have been described, namely non B-cell helper Tfh1 and the two B-helper cell subsets Tfh2 and Tfh17. We determined that circulating Tfh cells were elevated in CVID patients and skewed toward a Tfh1 profile. Interestingly, elevated levels of Tfh1 cells were significant only in patients harboring non-infectious complications regardless of the type of complication and inversely correlated with switched memory B cells. Moreover, CXCR3+ cells are increased in splenic CVID germinal centers. Our observations suggest that the altered balance in Tfh subsets in CVID is linked to a more severe disease.