RIPK2 and Bloom syndrome: Evidence that this reduced IRF4 level is directly related to defective NOD2 function came from Western blot studies of monocyte-derived dendritic cells from a patient with BS in which we showed that Blau patient cells express greatly reduced amounts of IRF4 both at baseline and following MDP or, to a lesser extent, following LPS stimulation; in addition, under the same conditions the patient DCs express decreased levels of RIPK2, particularly after MDP stimulation (Figure 9C).