IL-9-producing T cells: potential players in allergy and cancer

IL-9-producing CD4(+)T cells have been considered to represent a distinct T helper cell (T(H)cell) subset owing to their unique developmental programme in vitro, their expression of distinct transcription factors (including PU.1) and their copious production of IL-9. It remains debatable whether these cells represent a truly unique T(H)cell subset in vivo, but they are closely related to the T helper 2 (T(H)2) cells that are detected in allergic diseases. In recent years, increasing evidence has also indicated that IL-9-producing T cells may have potent abilities in eradicating advanced tumours, particularly melanomas. Here, we review the latest literature on the development of IL-9-producing T cells and their functions in disease settings, with a particular focus on allergy and cancer. We also discuss recent ideas concerning the therapeutic targeting of these cells in patients with chronic allergic diseases and their potential use in cancer immunotherapy. This Review covers our current understanding of the roles of IL-9-producing T cells in allergy and cancer. Should these cells be classified as a distinct IL-9-producing T helper cell subset? And can we therapeutically target them for the treatment of chronic allergic diseases and cancer?

Automated summary

IL-9-producing CD4(+)T cells are considered a unique subset of T helper cells, closely related to T(H)2 cells and potentially playing important roles in allergic diseases and cancer. Research suggests that these cells may have strong potential in treating late-stage tumors such as melanomas.