Figure 2.

Schematic diagram of macrophage subtypes. Allergen exposure (i.e. cockroach allergen) activates lung epithelial cells and innate immune cells to produce a variety of cytokines, which direct specific macrophage polarization subtype. M1 subtype is generally considered to be pro-inflammatory, M2a subtype is induced by IL-4 and IL-13, which are critical mediators of allergic inflammation. M2b and M2c subtypes predominately participate in tissue remodeling and fibrosis. BV (blood vessel), Mo (monocyte).