T helper (Th) 17 cells represent a novel subset of CD4+ T cells that are protective against extracellular microbes, but are responsible for autoimmune disorders in mice. However, their properties in humans are only partially known. We demonstrate the presence of Th17 cells, some of which produce both interleukin (IL)-17 and interferon (IFN)-γ (Th17/Th1), in the gut of patients with Crohn's disease. Both Th17 and Th17/Th1 clones showed selective expression of IL-23R, CCR6, and the transcription factor RORγt, and they exhibited similar functional features, such as the ability to help B cells, low cytotoxicity, and poor susceptibility to regulation by autologous regulatory T cells. Interestingly, these subsets also expressed the Th1-transcription factor T-bet, and stimulation of these cells in the presence of IL-12 down-regulated the expression of RORγt and the production of IL-17, but induced IFN-γ. These effects were partially inhibited in presence of IL-23. Similar receptor expression and functional capabilities were observed in freshly derived IL-17–producing peripheral blood and tonsillar CD4+ T cells. The demonstration of selective markers for human Th17 cells may help us to understand their pathogenic role. Moreover, the identification of a subset of cells sharing features of both Th1 and Th17, which can arise from the modulation of Th17 cells by IL-12, may raise new issues concerning developmental and/or functional relationships between Th17 and Th1.

STEM CELLS 2006;24: 386 -398

We demonstrate that CD161 is a highly up-regulated gene in human interleukin

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer‐reviewed by leading experts in the field, making this an essential research companion.

No abstract

Background: Coronavirus disease 19 (COVID-19) is an emerging infectious disease caused by SARS-CoV-2. Anti-viral immune response is crucial to achieve pathogen clearance, however in some patients an excessive and aberrant host immune response can lead to an acute respiratory distress syndrome. The comprehension of the mechanisms that regulate pathogen elimination, immunity, and pathology is essential to better characterize disease progression and widen the spectrum of therapeutic options. Methods: We performed a flow cytometric characterization of immune cells subsets from 30 COVID-19 patients and correlated these data with clinical outcomes. Results: COVID-19 patients showed decreased numbers of circulating T, B and NK cells, and exhibited a skewing of CD8+ T cells towards a terminally differentiated/senescent phenotype. In agreement, T CD4+, T CD8+ but also NK cells displayed reduced anti-viral cytokine production capability. Moreover, a reduced cytotoxic potential was identified in COVID-19 patients, particularly in those that required intensive care. The latter group of patients showed also increased serum IL-6 levels, that correlated to the frequency of granzyme-expressing NK cells. Off-label treatment with tocilizumab restored the cytotoxic potential of NK cells. Conclusion: In conclusion, the association between IL-6 serum levels and the impairment of cytotoxic activity suggests the possibility that targeting this cytokine may restore anti-viral mechanisms.

STEM CELLS 2008;26:279 -289 Disclosure of potential conflicts of interest is found at the end of this article.

Phenotypic markers, localization, functional activities, and mechanisms of action in vitro of CD4+CD25+ T cells, purified from postnatal human thymuses, were investigated. These cells showed poor or no proliferation in mixed lymphocyte culture (MLC), and suppressed in a dose-dependent fashion the proliferative response to allogeneic stimulation of CD4+CD25− thymocytes. Virtually all CD4+CD25+ thymocytes constitutively expressed cytoplasmic T lymphocyte antigen (CTLA)-4, surface tumor necrosis factor type 2 receptor (TNFR2), and CCR8. They prevalently localized to perivascular areas of fibrous septa and responded to the chemoattractant activity of CCL1/I-309, which was found to be produced by either thymic medullary macrophages or fibrous septa epithelial cells. After polyclonal activation, CD4+CD25+ thymocytes did not produce the cytokines interleukin (IL)-2, IL-4, IL-5, IL-13, interferon γ, and only a very few produced IL-10, but all they expressed on their surface CTLA-4 and the majority of them also transforming growth factor (TGF)-β1. The suppressive activity of these cells was contact dependent and associated with the lack of IL-2 receptor (IL-2R) α-chain (CD25) expression in target cells. Such a suppressive activity was partially inhibited by either anti–CTLA-4 or anti–TGF-β1, and was completely blocked by a mixture of these monoclonal antibodies, which were also able to restore in target T cells the expression of IL-2R α-chain and, therefore, their responsiveness to IL-2. These data demonstrate that CD4+CD25+ human thymocytes represent a population of regulatory cells that migrate in response to the chemokine CCL1/I-309 and exert their suppressive function via the inhibition of IL-2R α-chain in target T cells, induced by the combined activity of CTLA-4 and membrane TGF-β1.