Because antigen-presenting dendritic cells direct T-cell differentiation by producing Th2/Th17-inducing molecules (e.g., OX40L for Th2; IL-6, TGF-β and osteopontin for Th17), functional alteration of dendritic cells is suspected as a cause of insensitivity to steroid-based therapy as well as female predominance of asthma [31–33]. This evidence concerns the gene IL6 and asthma.