Enhancing comparative T cell receptor repertoire analysis in small biological samples through pooling homologous cell samples from multiple mice.

Accurate characterization and comparison of T cell receptor (TCR) repertoires from small biological samples present significant challenges. The main challenge is the low material input, which compromises the quality of bulk sequencing and hinders the recovery of sufficient TCR sequences for robust analyses. We aimed to address this limitation by implementing a strategic approach to pool homologous biological samples. Our findings demonstrate that such pooling indeed enhances the TCR repertoire coverage, particularly for cell subsets of constrained sizes, and enables accurate comparisons of TCR repertoires at different levels of complexity across T cell subsets with different sizes. This methodology holds promise for advancing our understanding of T cell repertoires in scenarios where sample size constraints are a prevailing concern.

Low-dose IL-2 shapes a tolerogenic gut microbiota that improves autoimmunity and gut inflammation.

Gut microbiota dysbiosis is associated with inflammatory bowel diseases and with cardiometabolic, neurological, and autoimmune diseases. Gut microbiota composition has a direct effect on the immune system, and vice versa, and it has a particular effect on Treg homeostasis. Low-dose IL-2 (IL-2LD) stimulates Tregs and is a promising treatment for autoimmune and inflammatory diseases. We aimed to evaluate the impact of IL-2LD on gut microbiota and correlatively on the immune system. We used 16S ribosomal RNA profiling and metagenomics to characterize gut microbiota of mice and humans treated or not with IL-2LD. We performed fecal microbiota transplantation (FMT) from IL-2LD-treated to naive recipient mice and evaluated its effects in models of gut inflammation and diabetes. IL-2LD markedly affected gut microbiota composition in mice and humans. Transfer of an IL-2-tuned microbiota by FMT protected C57BL/6J mice from dextran sulfate sodium-induced colitis and prevented diabetes in NOD mice. Metagenomic analyses highlighted a role for several species affected by IL-2LD and for microbial pathways involved in the biosynthesis of amino acids, short-chain fatty acids, and L-arginine. Our results demonstrate that IL-2LD induced changes in gut microbiota that are involved in the immunoregulatory effects of IL-2LD and suggest a crosstalk between Tregs and gut microbiota. These results provide potentially novel insight for understanding the mode of action of Treg-directed therapies.

Regulatory T lymphocytes/Th17 lymphocytes imbalance in autism spectrum disorders: evidence from a meta-analysis.

BACKGROUND: Immune system dysfunction has been proposed to play a critical role in the pathophysiology of autism spectrum disorders (ASD). Conflicting reports of lymphocyte subpopulation abnormalities have been described in numerous studies of patients with ASD. To better define lymphocytes abnormalities in ASD, we performed a meta-analysis of the lymphocyte profiles from subjects with ASD. METHODS: We used the PRISMA recommendations to query PubMed, Embase, PsychoINFO, BIOSIS, Science Direct, Cochrane CENTRAL, and Clinicaltrials.gov for terms related to clinical diagnosis of ASD and to lymphocytes' populations. We selected studies exploring lymphocyte subpopulations in children with ASD. The search protocol has been registered in the international Prospective Register of Systematic Reviews (CRD42019121473). RESULTS: We selected 13 studies gathering 388 ASD patients and 326 healthy controls. A significant decrease in the CD4+ lymphocyte was found in ASD patients compared to controls [- 1.51 (95% CI - 2.99; - 0.04) p = 0.04] (I2 = 96% [95% CI 94.6, 97.7], p < 0.01). No significant difference was found for the CD8+ T, B and natural killer lymphocytes. Considering the CD4+ subpopulation, there was a significant decrease in regulatory T lymphocytes (Tregs) in ASD patients (n = 114) compared to controls (n = 107) [- 3.09 (95% CI - 4.41; - 1.76) p = 0.0001]; (I2 = 90.9%, [95% CI 76.2, 96.5], p < 0.0001) associated with an increase oin the Th17 lymphocytes (ASD; n = 147 controls; n = 128) [2.23 (95% CI 0.79; 3.66) p = 0,002] (I2 = 95.1% [95% CI 90.4, 97.5], p < 0.0001). LIMITATIONS: Several factors inducing heterogeneity should be considered. First, differences in the staining method may be responsible for a part in the heterogeneity of results. Second, ASD population is also by itself heterogeneous, underlying the need of studying sub-groups that are more homogeneous. CONCLUSION: Our meta-analysis indicates defects in CD4+ lymphocytes, specifically decrease oin Tregs and increase in Th17 in ASD patients and supports the development of targeted immunotherapies in the field of ASD.

Impaired Activated/Memory Regulatory T Cell Clonal Expansion Instigates Diabetes in NOD Mice.

Regulatory T cell (Treg) insufficiency licenses the destruction of insulin-producing pancreatic ß-cells by autoreactive effector T cells (Teffs), causing spontaneous autoimmune diabetes in NOD mice. We investigated the contribution to diabetes of the T-cell receptor (TCR) repertoires of naive regulatory T cells (nTregs), activated/memory Tregs (amTregs), and CD4+ Teffs from prediabetic NOD mice and normal C57BL/6 (B6) mice. NOD mice amTreg and Teff repertoire diversity was unexpectedly higher than that of B6 mice. This was due to the presence of highly expanded clonotypes in B6 amTregs and Teffs that were largely lost in their NOD counterparts. Interleukin-2 (IL-2) administration to NOD mice restored such amTreg clonotype expansions and prevented diabetes development. In contrast, IL-2 administration only led to few or no clonotype expansions in nTregs and Teffs, respectively. Noteworthily, IL-2-expanded amTreg and nTreg clonotypes were markedly enriched in islet-antigen specific TCRs. Altogether, our results highlight the link between a reduced clonotype expansion within the activated Treg repertoire and the development of an autoimmune disease. They also indicate that the repertoire of amTregs is amenable to rejuvenation by IL-2.

Tfr cells lack IL-2Rα but express decoy IL-1R2 and IL-1Ra and suppress the IL-1-dependent activation of Tfh cells.

Follicular regulatory T (Tfr) cells from lymph node germinal centers control follicular helper T (Tfh) cell-dependent B cell activation. These scarce cells, often described and purified as CD25+ cells, are thought to be derived from thymic regulatory T (Treg) cells. However, we observed that mouse Tfr cells do not respond to interleukin-2 (IL-2), unlike Treg cells. Stringent immunophenotyping based on B cell lymphoma 6 (Bcl6), programmed cell death protein 1 (PD-1), and CXCR5 expression revealed that Tfr cells are actually CD25-, in mice and humans. Moreover, Tfr cell characterization based only on CXCR5 and PD-1 high expression without excluding CD25+ cells resulted in contamination with Treg cells. Transcriptome studies of CD4+CXCR5+PD-1+Bcl6+Foxp3+CD25- Tfr cells revealed that they express the IL-1 decoy receptor IL-1R2 and the IL-1 receptor antagonist IL-1Ra, whereas Tfh cells express the IL-1R1 agonist receptor. IL-1 treatment expanded Tfh cells in vivo and activated their production of IL-4 and IL-21 in vitro. Tfr cells suppressed the IL-1-induced activation of Tfh cells as efficiently as the IL-1 receptor antagonist Anakinra. Altogether, these results reveal an IL-1 axis in the Tfh cell control of B cell responses and an IL-2/IL-1 dichotomy for Treg cell control of effector T cells versus Tfr cell control of Tfh cells.

Treatment of Uveitis by In Situ Administration of Ex Vivo-Activated Polyclonal Regulatory T Cells.

CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cell therapy is a promising approach for the treatment of autoimmune diseases. To be effective, Treg cells should be in an activated state in the target tissue. This can be achieved by systemic administration of Ag-specific Treg cells, which are difficult to produce in conditions that can be translated to the clinic. In this paper, we propose an alternative approach consisting of in situ injection of preactivated polyclonal Treg cells that would exert bystander suppression in the target tissue. We show that polyclonal Treg cells suppressed uveitis in mice as efficiently as Ag-specific Treg cells but only when preactivated and administered in the vitreous. Uveitis control was correlated with an increase of IL-10 and a decrease of reactive oxygen species produced by immune cell infiltrates in the eye. Thus, our results reveal a new mechanism of Treg cell-mediated suppression and a new Treg cell therapy approach.

Sustained stimulation and expansion of Tregs by IL2 control autoimmunity without impairing immune responses to infection, vaccination and cancer.

Interleukin 2 (IL2) is the key cytokine supporting survival and function of regulatory T cells (Tregs). We recently reported that low-dose IL2 safely expands/stimulates Tregs and improves autoimmune conditions in humans. Further development of IL2 in autoimmune diseases will require chronic IL2 administration, which could affect beneficial effector immune responses regulated by Tregs. We used recombinant adeno-associated viral vector (rAAV)-mediated gene transfer to continuously release IL2 in mice and assessed its long-term effects on immune responses. A single rAAV-IL2 injection enabled sustained stimulation and expansion of Tregs without inducing Teff activation and prevented diabetes in NOD mice. After several weeks of IL2 production, mice responded normally to a viral challenge and to vaccination, and had pregnancies with offspring that developed normally. They showed no change in the occurrence and growth of chemically-induced tumors. Altogether, chronic low-dose IL2 treatment does not affect beneficial effector immune responses at doses that prevent autoimmune diabetes.

Limitations of IL-2 and rapamycin in immunotherapy of type 1 diabetes.

Administration of low-dose interleukin-2 (IL-2) alone or combined with rapamycin (RAPA) prevents hyperglycemia in NOD mice. Also, low-dose IL-2 cures recent-onset type 1 diabetes (T1D) in NOD mice, partially by boosting pancreatic regulatory T cells (Treg cells). These approaches are currently being evaluated in humans. Our objective was to study the effect of higher IL-2 doses (250,000-500,000 IU daily) as well as low-dose IL-2 (25,000 IU daily) and RAPA (1 mg/kg daily) (RAPA/IL-2) combination. We show that, despite further boosting of Treg cells, high doses of IL-2 rapidly precipitated T1D in prediabetic female and male mice and increased myeloid cells in the pancreas. Also, we observed that RAPA counteracted IL-2 effects on Treg cells, failed to control IL-2-boosted NK cells, and broke IL-2-induced tolerance in a reversible way. Notably, the RAPA/IL-2 combination failure to cure T1D was associated with an unexpected deleterious effect on glucose homeostasis at multiple levels, including ß-cell division, glucose tolerance, and liver glucose metabolism. Our data help to understand the therapeutic limitations of IL-2 alone or RAPA/IL-2 combination and could lead to the design of improved therapies for T1D.

Fetal pancreas transplants are dependent on prolactin for their development and prevent type 1 diabetes in syngeneic but not allogeneic mice.

Transplantation of adult pancreatic islets has been proposed to cure type 1 diabetes (T1D). However, it is rarely considered in the clinic because of its transient effect on disease, the paucity of donors, and the requirement for strong immunosuppressive treatment to prevent allogeneic graft rejection. Transplantation of fetal pancreases (FPs) may constitute an attractive alternative because of potential abundant donor sources, possible long-term effects due to the presence of stem cells maintaining tissue integrity, and their supposed low immunogenicity. In this work, we studied the capacity of early FPs from mouse embryos to develop into functional pancreatic islets producing insulin after transplantation in syngeneic and allogeneic recipients. We found that as few as two FPs were sufficient to control T1D in syngeneic mice. Surprisingly, their development into insulin-producing cells was significantly delayed in male compared with female recipients, which may be explained by lower levels of prolactin in males. Finally, allogeneic FPs were rapidly rejected, even in the context of minor histocompatibility disparities, with massive graft infiltration with T and myeloid cells. This work suggests that FP transplantation as a therapeutic option of T1D needs to be further assessed and would require immunosuppressive treatment.

IL-2 reverses established type 1 diabetes in NOD mice by a local effect on pancreatic regulatory T cells.

Regulatory T cells (T reg cells) play a major role in controlling the pathogenic autoimmune process in type 1 diabetes (T1D). Interleukin 2 (IL-2), a cytokine which promotes T reg cell survival and function, may thus have therapeutic efficacy in T1D. We show that 5 d of low-dose IL-2 administration starting at the time of T1D onset can reverse established disease in NOD (nonobese diabetic) mice, with long-lasting effects. Low-dose IL-2 increases the number of T reg cells in the pancreas and induces expression of T reg cell-associated proteins including Foxp3, CD25, CTLA-4, ICOS (inducible T cell costimulator), and GITR (glucocorticoid-induced TNF receptor) in these cells. Treatment also suppresses interferon gamma production by pancreas-infiltrating T cells. Transcriptome analyses show that low-dose IL-2 exerts much greater influence on gene expression of T reg cells than effector T cells (T eff cells), suggesting that nonspecific activation of pathogenic T eff cells is less likely. We provide the first preclinical data showing that low-dose IL-2 can reverse established T1D, suggesting that this treatment merits evaluation in patients with T1D.