Fig. 1.

Summary of the events and cell types involved in the pathogenesis of chronic rhinosinusitis with nasal polyps. Immune cells shown on the top of the figure are elevated in polyp tissue from most European and American patients and a subset of Asian patients. Recent studies discussed in the text provide the basis for a model in which local expansion of T cells, B cells and plasma cells occurs with the help of local dendritic cells, resulting in the production of cytokines and immunoglobulins at high levels in the tissue (top left). Recruitment and/or activation of effector cells, shown on the top right, is likely a consequence of the activation of adaptive immune cells, tissue cells (e.g. epithelium and endothelium) and innate lymphoid cells. Activation of structural cells can contribute to cellular recruitment, leak and activation of plasma proteins, deposition of fibrin and modification of the extracellular matrix. The actions of both the immune and the structural cells lead to tissue remodelling, as summarized in part on the lower right.