Trypanosoma cruzi-specific IFN-γ-producing cells in chronic Chagas disease associate with a functional IL-7/IL-7R axis.

BACKGROUND: The severity of cardiac disease in chronic Chagas disease patients is associated with different features of T-cell exhaustion. Here, we assessed whether the ability of T cells to secrete IFN-γ in response to T. cruzi was linked to disruption in immune homeostasis and inflammation in patients with chronic Chagas disease. METHODOLOGY/PRINCIPAL FINDINGS: PBMCs from chronic Chagas disease patients and uninfected controls were examined for frequencies of T. cruzi-responsive IFN-γ-producing cells by ELISPOT and cellular expression and function of IL-7R using flow cytometry. Serum levels of IL-7, IL-21, IL-27, soluble IL-7R, and inflammatory cytokines were also evaluated by ELISA or CBA techniques. Patients possessing T. cruzi-specific IFN-γ-producing cells (i.e. IFN-γ producers) had higher levels of memory T cells capable of modulating the alpha chain of IL-7R and an efficient response to IL-7 compared to that in patients lacking (i.e. IFN-γ nonproducers) parasite-specific T-cell responses. IFN-γ producers also showed low levels of soluble IL-7R, high basal expression of Bcl-2 in T cells and low basal frequencies of activated CD25+ T cells. Modulation of IL-7R was inversely associated with serum IL-6 levels and positively associated with serum IL-8 levels. Circulating IL-21 and IL-27 levels were not associated with the frequency of IFN-γ producing cells but were reduced in less severe clinical forms of the disease. In vitro stimulation of PBMCs with IL-7 or IL-27 enhanced IFN-γ production in IFN-γ producers but not in IFN-γ nonproducers. CONCLUSIONS/SIGNIFICANCE: Alterations of the IL-7/IL-7R axis and in the levels of inflammatory cytokines were linked to impaired T. cruzi-specific IFN-γ production. These alterations might be responsible of the process of immune exhaustion observed in chronic Chagas disease.

B-1 cells and B-1 cell precursors prompt different responses to Wnt signaling.

Recently several studies demonstrated a role for the Wnt pathway in lymphocyte development and self-renewal of hematopoietic stem cells (HSCs). B-1 cells constitute a separate lineage of B lymphocytes, originating during fetal hematopoiesis, expressing lymphoid and myeloid markers and possessing self-renewal ability, similar to early hematopoietic progenitors and HSCs. A plethora of studies have shown an important role for the evolutionary conserved Wnt pathway in the biology of HSCs and T lymphocyte development. Our previous data demonstrated abundant expression of Wnt pathway components by B-1 cells, including Wnt ligands and receptors. Here we report that the canonical Wnt pathway is activated in B-1 cell precursors, but not in mature B-1 cells. However, both B-1 precursors and B-1 cells are able to respond to Wnt ligands in vitro. Canonical Wnt activity promotes proliferation of B-1 cells, while non-canonical Wnt signals induce the expansion of B-1 precursors. Interestingly, using a co-culture system with OP9 cells, Wnt3a stimulus supported the generation of B-1a cells. Taking together, these results indicate that B-1 cells and their progenitors are differentially responsive to Wnt ligands, and that the balance of activation of canonical and non-canonical Wnt signaling may regulate the maintenance and differentiation of different B-1 cell subsets.

Fat-associated lymphoid cluster in Cyprinus carpio: Characterisation and its relation with peritoneal haemangiosarcoma.

FALC cells are natural helper cells producing Th2-type cytokines, which express c-kit, Sca-1, IL7R and CD45 in mouse and human. These cells are involved in allergic responses and contribute to the inflammatory reactions of adipose tissue; however, a lack of information prevails about the presence of these cells in other species. The aim of the study was to identify and characterise FALC cells in the common carp (Cyprinus carpio) using immunohistochemistry and molecular biology techniques as well as to explore their relationships with their microenvironment. Histological description of the FALC was performed using H&E and polyclonal antibodies were used against cell-surface markers such as c-kit, Sca-1 and CD45. Furthermore, gene expression of c-kit, Sca-1 and IL7R was assessed. C. carpio FALC cells express the same surface markers reported in FALC of the mouse at both the pre- and post-transcriptional level. By exposure to the soluble fraction of helminths, FALC cells produce abundant Th2 cytokines (IL-5, IL-6 and IL-13) but do not synthesise IL-1α. Additionally, FALC cells probably participate in vascular remodelling of the intestine vessels, inducing tumours because a malignant haemangiosarcoma in the peritoneal cavity was found. In this tumour, abundant FALC with their characteristic cell-surface markers were detected. The findings of this study suggest the involvement of some proto-oncogenes such as c-kit and Sca-1, and the deregulation of Src kinases modulated by CD45 present in C. carpio FALC with the ontogeny of peritoneal haemangiosarcoma in this fish species.

Interleukin 7 plays a role in T lymphocyte apoptosis inhibition driven by mesenchymal stem cell without favoring proliferation and cytokines secretion.

Since 2004, when a case report describing the use of human mesenchymal stem cells (hMSCs) infusion as a therapy for GVHD after bone marrow transplantation, a new perspective in MSC function emerged. Since then hMSCs immunomodulatory potential became the target of several studies. Although great progress has been made in our understanding of hMSCs, their effect on T cell remains obscure. Our study has confirmed the already described effect of hMSCs on lymphocytes proliferation and survival. We also show that the impairment of lymphocyte proliferation and apoptosis is contact-independent and occurs in a prostaglandin-independent manner. A potential correlation between IL-7 and hMSCs effect is suggested, as we observed an increase in IL-7 receptors (CD127) on lymphocyte membrane in MSC presence. Additionally, blocking IL-7 in hMSCs-lymphocytes co-cultures increased lymphocytes apoptosis and we also have demonstrated that hMSCs are able to produce this interleukin. Moreover, we found that during Th1/Th17 differentiation in vitro, hMSCs presence leads to Th1/Th17 cells with reduced capacity of INF-y and IL-17 secretion respectively, regardless of having several pro-inflammatory cytokines in culture. We did not confirm an increment of Treg in these cultures, but a reduced percentage of INF-y/IL-17 secreting cells was observed, suggesting that the ratio between anti and pro-inflammatory cells changed. This changed ratio is very important to GvHD therapy and links hMSCs to an anti-inflammatory role. Taken together, our findings provide important preliminary results on the lymphocyte pathway modulated by MSCs and may contribute for developing novel treatments and therapeutic targets for GvHD and others autoimmune diseases.

Oncogenic IL7R gain-of-function mutations in childhood T-cell acute lymphoblastic leukemia.

Interleukin 7 (IL-7) and its receptor, formed by IL-7Rα (encoded by IL7R) and γc, are essential for normal T-cell development and homeostasis. Here we show that IL7R is an oncogene mutated in T-cell acute lymphoblastic leukemia (T-ALL). We find that 9% of individuals with T-ALL have somatic gain-of-function IL7R exon 6 mutations. In most cases, these IL7R mutations introduce an unpaired cysteine in the extracellular juxtamembrane-transmembrane region and promote de novo formation of intermolecular disulfide bonds between mutant IL-7Rα subunits, thereby driving constitutive signaling via JAK1 and independently of IL-7, γc or JAK3. IL7R mutations induce a gene expression profile partially resembling that provoked by IL-7 and are enriched in the T-ALL subgroup comprising TLX3 rearranged and HOXA deregulated cases. Notably, IL7R mutations promote cell transformation and tumor formation. Overall, our findings indicate that IL7R mutational activation is involved in human T-cell leukemogenesis, paving the way for therapeutic targeting of IL-7R-mediated signaling in T-ALL.