Moreover, allergic asthma under theinfluence of Th2-cytokines (IL-4, IL-13) and TGF-β increasesthe arginase expression, which raises the L-ornithine, polyaminesand L-proline production, which participates in airwayremodeling, by inducing cell proliferation, and enhanced collagenproduction and fibrosis (see the Figure) (Meurs et al.,2019). Here, TGFB1 is linked to allergic asthma.