CD28/CTLA-4/B7 and CD40/CD40L costimulation and activation of regulatory T cells

Differential transcriptional and functional properties of regulatory T cells in HIV-infected individuals on antiretroviral therapy and long-term non-progressors

Objectives

Regulatory T cells (Tregs) are widely recognised as a subset of CD4⁺CD25⁺FOXP3⁺ T cells that have a key role in maintaining immune homeostasis. The impact of HIV‐1 infection on immunological properties and effector functions of Tregs has remained the topic of debate and controversy. In the present study, we investigated transcriptional profile and functional properties of Tregs in HIV‐1‐infected individuals either receiving antiretroviral therapy (ART, n = 50) or long‐term non‐progressors (LTNPs, n = 24) compared to healthy controls (HCs, n = 38).

Methods

RNA sequencing (RNAseq), flow cytometry‐based immunophenotyping and functional assays were performed to study Tregs in different HIV cohorts.

Results

Our RNAseq analysis revealed that Tregs exhibit different transcriptional profiles in HIV‐infected individuals. While Tregs from patients on ART upregulate pathways associated with a more suppressive (activated) phenotype, Tregs in LTNPs exhibit upregulation of pathways associated with impaired suppressive properties. These observations may explain a higher propensity for autoimmune diseases in LTNPs. Also, we found substantial upregulation of HLA‐F mRNA and HLA‐F protein in Tregs from HIV‐infected subjects compared to healthy individuals. These observations highlight a potential role for this non‐classical HLA in Tregs in the context of HIV infection, which should be investigated further in other chronic viral infections and cancer.

Conclusion

Our study has provided a novel insight into Tregs at the transcriptional and functional levels in different HIV‐infected groups.

Crohn's Disease Increases the Mesothelial Properties of Adipocyte Progenitors in the Creeping Fat

Our understanding of the interplay between human adipose tissue and the immune system is limited. The mesothelium, an immunologically active structure, emerged as a source of visceral adipose tissue. After investigating the mesothelial properties of human visceral and subcutaneous adipose tissue and their progenitors, we explored whether the dysfunctional obese and Crohn's disease environments influence the mesothelial/mesenchymal properties of their adipocyte precursors, as well as their ability to mount an immune response. Using a tandem transcriptomic/proteomic approach, we evaluated the mesothelial and mesenchymal expression profiles in adipose tissue, both in subjects covering a wide range of body-mass indexes and in Crohn's disease patients. We also isolated adipose tissue precursors (adipose-derived stem cells, ASCs) to assess their mesothelial/mesenchymal properties, as well as their antigen-presenting features. Human visceral tissue presented a mesothelial phenotype not detected in the subcutaneous fat. Only ASCs from mesenteric adipose tissue, named creeping fat, had a significantly higher expression of the hallmark mesothelial genes mesothelin (MSLN) and Wilms' tumor suppressor gene 1 (WT1), supporting a mesothelial nature of these cells. Both lean and Crohn's disease visceral ASCs expressed equivalent surface percentages of the antigen-presenting molecules human leucocyte antigen-DR isotype (HLA-DR) and CD86. However, lean-derived ASCs were predominantly HLA-DR ^dim, whereas in Crohn's disease, the HLA-DR ^bright subpopulation was increased 3.2-fold. Importantly, the mesothelial-enriched Crohn's disease precursors activated CD4⁺ T-lymphocytes. Our study evidences a mesothelial signature in the creeping fat of Crohn's disease patients and its progenitor cells, the latter being able to present antigens and orchestrate an immune response.