TLR2 and hypersensitivity pneumonitis: Our data are consistent with accumulated evidence from in vitro studies confirming that the activation of TLR2 signaling pathway on CD4+ cells promotes the development of Th17 immune response in a number of pathologies, including acute disseminated encephalomyelitis [33], multiple sclerosis [37], systemic lupus erythematosus [36], hypersensitivity pneumonitis [34], and hepatitis B [35, 38].