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.

SummaryThe effects exerted on the in vitro development of antigen-specific T cell lines and T cell clones by addition or neutralization of interleukin 12 (I1:12) in lymphocyte bulk culture were examined. T cell lines specific for Dermatophagoides pteronyssinus group I (Der p I) derived in the presence of I1:12 exhibited reduced ability to produce I1:4 and increased ability to produce interferon "/(IFN-3~), and developed into Der p I-specific CD4 § T cell clones showing a T helper type 0 (Th0)-or Thl-, instead of Th2-, like cytokine profile. In contrast, purified protein derivative (PPD)-specific T cell lines derived in the presence of anti-I1:12 antibody exhibited an increased ability to produce I1:4 and developed into PPD-specific CD4 + T cell clones showing a Th0-, instead of Thl-, like profile. The influence of IL-12 on the cytokine secretion profile of Der p I-specific T cell lines was not prevented by addition to lymphocyte bulk cultures of anti-IFN-y antibody, but could be at least partially inhibited by the removal from bulk cultures of CD16 + cells. Thus, IL-12 and CD16 + cells appear to have inhibitory effects on the development of IL-4-producing cells and to play an inductive role in promoting Thl-like responses.

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

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.

We have established a large panel of T-cell clones (TCCs) specific for Dermatophagoides pteronyssinus and Loliumperenne group I grass pollen allergens (total, 61) and for tetanus toxoid and protein purified derivative bacterial antigens (total, 38) from the peripheral blood of two atopic Individuals and then analyzed their ability to produce interleukin 4 (IL-4), IL-5, and interferon y (IFN-y). Upon stimulation with phorbol 12-myristate 13-acetate plus anti-CD3 antibody, the great majority of TCCs specific for bacterial components was able to produce both IL-4 and IFN-y, whereas most D. pteronyssinus-and L. perenne group I-specific TCCs produced IL-4, but no, or limited, IFN-y. Moreover, the mean amounts of IL-4 and IFN-y released by allergen-specific TCCs were significantly higher and lower, respectively, than the mean amounts produced by TCCs specific for bacterial components. Under the same experimental conditions, virtually all allergen-specific TCCs, but only one-third of tested TCCs specific for bacterial components, expressed IL-5 RNA and secreted IL-5 in their supernatants. Eighteen TCCs (nine specific for allergens and nine specific for bacterial compo-

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SummaryInterleukin 12 facilitates the generation of a T helper type 1 (Thl) response, with high interferon 3' (IFN-3') production, while inhibiting the generation of IL-4-producing Th2 calls in polyclonal cultures of both human and murine T cells and in vivo in the mouse. In this study, we analyzed the effect of IL-12, present during cloning of human T cells, on the cytokine profile of the clones. The culture system used allows growth of clones from virtually every T cell, and thus excludes the possibility that selection of precommitted Th cell precursors plays a role in determining characteristics of the clones. IL-12 present during the cloning procedures endowed both CD4 + and CD8 + clones with the ability to produce IFN-3" at levels severalfold higher than those observed in clones generated in the absence of IL-12. This priming was stable because the high levels of IFN-3' production were maintained when the clones were cultured in the absence of IL-12 for 11 d. The CD4 + and some of the CD8 + clones produced variable amounts of IL-4. Unlike IFN-3', IL-4 production was not significantly different in clones generated in the presence or absence of IL-12. These data suggest that IL-12 primes the done progenitors, inducing their differentiation to high IFN-3'-producing clones. The suppression of IL-4-producing cells observed in polyclonally generated T cells in vivo and in vitro in the presence of IL-12 is not observed in this donal model, suggesting that the suppression depends more on positive selection of non-IL-4-producing cells than on differentiation of individual clones. However, antigen-specific established Th2 clones that were unable to produce IFN-3, with any other inducer did produce IFN-3" at low but significant levels when stimulated with IL-12 in combination with specific antigen or insoluble anti-CD3 antibodies. This induction of IFN-3' gene expression was transient, because culture of the established clones with IL-12 for up to 1 wk did not convert them into IFN-3" producers when stimulated in the absence of IL-12. These results suggest that Th clones respond to IL-12 treatment either with a stable priming for IFN-3' production or with only a transient low level expression of the IFN-3" gene, depending on their stage of differentiation. ecent work from our and other laboratories (1-5) has shown that human CD4 + Th cell clones, in analogy to the murine system (6, 7), can be subdivided into at least three distinct functional subsets based on their cytokine secretion profile. One type of CD4 § done (Thl) produces IL-2, IFN-3`, and TNF-j3, but not IL-4 or IL-5; a second type (Th2) produces IL-4 and IL-5, but not IL-2, IFN-3`, or TNF-B; R. Manetti and F. Gerosa contributed equally to this work. and a third type (Th0) produces both Thl-and Th2-type cytokines (1,3,5,6). Although most CD8 + human T cell dones exhibit a Thl-like cytokine profile (3, 5), some CD8 + clones showing a Th2-1ike phenotype have also been described (s, 9).Several factors can affect the development of Thl or Th2 responses both in v...