FIG. 3.

Role of MMPs in adaptive immunity. In response to inhaled allergens, Th2 inflammatory cells home to the lung and initiate allergic lung disease that can manifest in many pathological features such as accumulation of eosiniphils, basophils, and neutrophils; increases in mucus production; goblet cell metaplasia; and narrowing of the airways. Increases in concentration of interleukin (IL)-4 and IL-13, the canonical Th2 cytokines, also orchestrate upregulation of MMPs in the lung mesenchymal cells (MMP2, MMP3), hematopoietic cells (MMP9, MMP12), and epithelial cells (MMP7). In experimental models where MMPs are inhibited or in mice deficient in MMP2, MMP9, or MMP2/MMP9 there is an accumulation of inflammatory cells in the lung parenchyma and that predisposes mice to death from asphyxiation (see Refs. ⁴⁸, ⁴⁹, ⁸⁸, ¹⁷⁰, ¹⁸⁶).