Highlights of IMMUNOLOGY2026™ - Invited Program Recordings-Counting to 9: the amazing adventures of the 9th interleukin

Video Transcription

Video Summary

The lecture introduced Mark Kaplan, a major immunologist whose work has shaped understanding of cytokine signaling and T helper cell biology. Kaplan focused on IL-9, a cytokine with complex, context-dependent roles in allergy, autoimmunity, cancer, and infection. He traced IL-9 research from its discovery to renewed interest after the identification of TH9 cells and IL-9-responsive innate lymphoid and myeloid cells.<br /><br />He described how TH2 cells are more heterogeneous than traditionally thought, with transcription factors like PU.1 helping control which cytokines individual cells produce. His lab showed that PU.1 also regulates IL-9 production in TH9 cells. He then highlighted evidence that IL-9-producing cells can be both classical TH9 cells and polyfunctional tissue-resident memory T cells involved in allergic recall responses.<br /><br />Kaplan also showed that IL-9 acts on multiple target cells, including mast cells and macrophages in allergic lung inflammation, and epithelial cells and macrophages in bladder infection. In the lung, IL-9 promotes asthma-like inflammation, while in the bladder it supports host defense against uropathogenic E. coli. His central message was that IL-9 biology depends heavily on tissue context, receptor expression, and disease state, making it both a challenging and potentially powerful therapeutic target.

Keywords

Mark Kaplan

IL-9

TH9 cells

cytokine signaling

T helper cell biology

allergic inflammation

mast cells

tissue context