Furthermore, conventional housing conditions (e.g., Helicobacter bilis) may influence the clinical course of colitis in MDR1α-deficient mice.191,192 It remains to be directly shown whether selected microbial species due to changes of the commensal composition may subvert host immune responses in the context of MDR1α deficiency, thus possibly allowing pathogenic hyperactivation of TLR4 (and other TLRs). The gene discussed is TLR4; the disease is colitis.