TLR4 and infection: Although genetic associations between TLR2, TLR4 and NOD2 polymorphisms with susceptibility to infections on the one hand (Schröder and Schumann 2005; Tekin et al. 2012; van Well et al. 2013), and BD (as discussed above) on the other have been independently reported in the literature, the influence of interaction between a particular infection and variability of the innate immune system on BD phenotype remains to be tested.