HMOX1 and Behcet disease: Kirino et al. reported that Toll-like receptor 4 (TLR4), which mediates activation of the innate immune system, was upregulated with a reduction in the anti-inflammatory enzyme heme oxygenase (HO)-1 in peripheral blood mononuclear cells in patients with BD, suggesting the involvement of innate immunity in the pathogenesis of BD [62].