Systemic inflammatory Th1 cytokines during Trypanosoma cruzi infection disrupt the typical anatomical cell distribution and phenotypic/functional characteristics of various cell subsets within the thymus.

The thymus plays a crucial role in T cell differentiation, a complex process influenced by various factors such as antigens, the microenvironment and thymic architecture. The way the thymus resolves infections is critical, as chronic persistence of microbes or inflammatory mediators can obstruct the differentiation. Here, we illustrate that following inflammatory T helper 1 infectious processes like those caused by Candida albicans or Trypanosoma cruzi, single positive thymocytes adopt a mature phenotype. Further investigations focused on T. cruzi infection, reveal a substantial existence of CD44+ cells in both the cortical and medullary areas of the thymus at the onset of infection. This disturbance coincides with heightened interferon gamma (IFNγ) production by thymocytes and an increased cytotoxic capacity against T. cruzi-infected macrophages. Additionally, we observe a reduced exportation capacity in T. cruzi-infected mice. Some alterations can be reversed in IFNγ knockout mice (KO). Notably, the majority of these effects can be replicated by systemic expression of interleukin (IL)-12+IL-18, underlining the predominantly inflammatory rather than pathogen-specific nature of these phenomena. Understanding the mechanisms through which systemic inflammation disrupts normal T cell development, as well as subsequent T cell exportation to secondary lymphoid organs (SLO) is pivotal for comprehending susceptibility to diseases in different pathological scenarios.

Human Effectors of Acute and Chronic GVHD Overexpress CD83 and Predict Mortality.

PURPOSE: Acute and chronic GVHD remain major causes of transplant-related morbidity and mortality (TRM) after allogeneic hematopoietic cell transplantation (alloHCT). We have shown CD83 chimeric antigen receptor (CAR) T cells prevent GVHD and kill myeloid leukemia cell lines. In this pilot study, we investigate CD83 expression on GVHD effector cells, correlate these discoveries with clinical outcomes, and evaluate critical therapeutic implications for transplant recipients. EXPERIMENTAL DESIGN: CD83 expression was evaluated among circulating CD4+ T cells, B-cell subsets, T follicular helper (Tfh) cells, and monocytes from patients with/without acute or chronic GVHD (n = 48 for each group), respectively. CD83 expression was correlated with survival, TRM, and relapse after alloHCT. Differential effects of GVHD therapies on CD83 expression was determined. RESULTS: CD83 overexpression on CD4+ T cells correlates with reduced survival and increased TRM. Increased CD83+ B cells and Tfh cells, but not monocytes, are associated with poor posttransplant survival. CD83 CAR T eliminate autoreactive CD83+ B cells isolated from patients with chronic GVHD, without B-cell aplasia as observed with CD19 CAR T. We demonstrate robust CD83 antigen density on human acute myeloid leukemia (AML), and confirm potent antileukemic activity of CD83 CAR T in vivo, without observed myeloablation. CONCLUSIONS: CD83 is a promising diagnostic marker of GVHD and warrants further investigation as a therapeutic target of both GVHD and AML relapse after alloHCT.

Exploring the immunomodulatory role of virtual memory CD8+ T cells: Role of IFN gamma in tumor growth control.

Virtual memory CD8+ T cells (TVM) have been described as cells with a memory-like phenotype but without previous antigen (Ag) exposure. TVM cells have the ability to respond better to innate stimuli rather than by TCR engagement, producing large amounts of interferon gamma (IFNγ) after stimulation with interleukin (IL)-12 plus IL-18. As a result of the phenotypic similarity, TVM cells have been erroneously included in the central memory T cell subset for many years. However, they can now be discriminated via the CD49d receptor, which is up-regulated only on conventional memory T cells (TMEM) and effector T cells (TEFF) after specific cognate Ag recognition by a TCR. In this work we show that systemic expression of IL-12 plus IL-18 induced an alteration in the normal TVM vs TMEM/TEFF distribution in secondary lymphoid organs and a preferential enrichment of TVM cells in the melanoma (B16) and the pancreatic ductal adenocarcinoma (KPC) tumor models. Using our KPC bearing OT-I mouse model, we observed a significant increase in CD8+ T cell infiltrating the tumor islets after IL-12+IL-18 stimulation with a lower average speed when compared to those from control mice. This finding indicates a stronger interaction of T cells with tumor cells after cytokine stimulation. These results correlate with a significant reduction in tumor size in both tumor models in IL-12+IL-18-treated OT-I mice compared to control OT-I mice. Interestingly, the absence of IFNγ completely abolished the high antitumor capacity induced by IL-12+IL-18 expression, indicating an important role for these cytokines in early tumor growth control. Thus, our studies provide significant new information that indicates an important role of TVM cells in the immune response against cancer.

Virtual Memory CD8+ T Cells: Origin and Beyond.

The presence of CD8+ T cells with a memory phenotype in nonimmunized mice has been noted for decades, but it was not until about 2 decades ago that they began to be studied in greater depth. Currently called virtual memory CD8+ T cells, they consist of a heterogeneous group of cells with memory characteristics, without any previous contact with their specific antigens. These cells were identified in mice, but a few years ago, a cell type with characteristics equivalent to the murine ones was described in healthy humans. In this review, we address the different aspects of its biology mainly developed in murine models and what is currently known about its cellular equivalent in humans.

Safety levels of systemic IL-12 induced by cDNA expression as a cancer therapeutic.

Aim: The aim of this work is to utilize a gene expression procedure to safely express systemic IL-12 and evaluate its effects in mouse tumor models. Materials & methods: Secondary lymphoid organs and tumors from EL4 and B16 tumor-bearing mice were analyzed by supervised and unsupervised methods. Results: IL-12 cDNA induced systemic IL-12 protein levels lower than the tolerated dose in patients. Control of tumor growth was observed in subcutaneous B16 and EL4 tumors. Systemic IL-12 expression induced a higher frequency of both total tumor-infiltrated CD45+ cells and proliferative IFN-γ+CD8+ T cells along with a lower frequency of CD4+FOXP3+ and CD11b+Gr-1+ cells. Conclusion: This approach characterizes the systemic effects of IL-12, helping to improve treatment of metastases or solid tumors.

Lay abstract IL-12 has emerged as a potent cytokine in mediating antitumor activity in preclinical models of cancer. However, this antitumor response has not yet been translated into the clinic because of toxic side effects. The aim of our work is to analyze the effects of IL-12 in mouse tumor models. We demonstrate that one injection of IL-12 cDNA can induce systemic IL-12 levels in serum even lower than the tolerated dose in patients. At this dose, an efficient control of tumor growth can be observed. We found a higher frequency of both total tumor-infiltrated leukocytes and IFN-γ-producing CD8⁺ T cells along with a lower frequency of regulatory CD4⁺FOXP3⁺ and CD11b⁺Gr1⁺ cells. Our work demonstrates that IL-12 cDNA can safely be used to treat cancer.

Thymic expression of IL-4 and IL-15 after systemic inflammatory or infectious Th1 disease processes induce the acquisition of "innate" characteristics during CD8+ T cell development.

Innate CD8+ T cells express a memory-like phenotype and demonstrate a strong cytotoxic capacity that is critical during the early phase of the host response to certain bacterial and viral infections. These cells arise in the thymus and depend on IL-4 and IL-15 for their development. Even though innate CD8+ T cells exist in the thymus of WT mice in low numbers, they are highly enriched in KO mice that lack certain kinases, leading to an increase in IL-4 production by thymic NKT cells. Our work describes that in C57BL/6 WT mice undergoing a Th1 biased infectious disease, the thymus experiences an enrichment of single positive CD8 (SP8) thymocytes that share all the established phenotypical and functional characteristics of innate CD8+ T cells. Moreover, through in vivo experiments, we demonstrate a significant increase in survival and a lower parasitemia in mice adoptively transferred with SP8 thymocytes from OT I-T. cruzi-infected mice, demonstrating that innate CD8+ thymocytes are able to protect against a lethal T. cruzi infection in an Ag-independent manner. Interestingly, we obtained similar results when using thymocytes from systemic IL-12 + IL-18-treated mice. This data indicates that cytokines triggered during the acute stage of a Th1 infectious process induce thymic production of IL-4 along with IL-15 expression resulting in an adequate niche for development of innate CD8+ T cells as early as the double positive (DP) stage. Our data demonstrate that the thymus can sense systemic inflammatory situations and alter its conventional CD8 developmental pathway when a rapid innate immune response is required to control different types of pathogens.