Human TH9 cells are skin-tropic and have autocrine and paracrine proinflammatory capacity.

T helper type 9 (TH9) cells can mediate tumor immunity and participate in autoimmune and allergic inflammation in mice, but little is known about the TH9 cells that develop in vivo in humans. We isolated T cells from human blood and tissues and found that most memory TH9 cells were skin-tropic or skin-resident. Human TH9 cells coexpressed tumor necrosis factor-α and granzyme B and lacked coproduction of TH1/TH2/TH17 cytokines, and many were specific for Candida albicans. Interleukin-9 (IL-9) production was transient and preceded the up-regulation of other inflammatory cytokines. Blocking studies demonstrated that IL-9 was required for maximal production of interferon-γ, IL-9, IL-13, and IL-17 by skin-tropic T cells. IL-9-producing T cells were increased in the skin lesions of psoriasis, suggesting that these cells may contribute to human inflammatory skin disease. Our results indicate that human TH9 cells are a discrete T cell subset, many are tropic for the skin, and although they may function normally to protect against extracellular pathogens, aberrant activation of these cells may contribute to inflammatory diseases of the skin.

Scientists’ situated knowledge: Strong objectivity in transdisciplinarity

Although transdisciplinary research has started addressing important epistemological challenges, as evidenced by the discussion about ‘mode 2’ knowledge production, its relation with postulations of ‘scientific objectivity’ is not yet well clarified. A common way of dealing with the epistemological challenge of situated knowledge production, as proposed by transdisciplinarity, is to point to the fundamental aspect of reflexivity. But reflexivity also includes being aware that power and control over the object is derived from the social position of researchers, an issue not often explicitly discussed in transdisciplinary research. Reflexivity thus represents an important but insufficient principle for guaranteeing appropriate levels of self-reflection within a process of knowledge coproduction. We therefore hypothesize that transdisciplinary research could greatly benefit from feminist scientific tradition, in particular the insights of standpoint theory and the concept of ‘strong objectivity’. We analyse, and reflect upon, how a recent transdisciplinary research initiative – conducted together with civil society organizations in (CSOs) in six countries: Bangladesh, Bolivia, Brazil, Burkina Faso, Ecuador and India – has benefited from the use of ‘strong objectivity’. We analyse how the social position of all stakeholders, including ourselves as the scientific actors in this initiative, influence the process and conditions of transdisciplinary knowledge co-production, and we discuss how power and control by scientists affects the process and conditions of interaction. Thereby we argue for the necessity of explicitly assuming sides in contested contexts for reaching objectivity in transdisciplinary research.