Intestinal luminal conversion of histidine to histamine by the probiotic L. reuteri activates the mouse histamine receptor H2R which subsequently results in suppression of IL-6 and IL-1β expression as well as of acute inflammation in TNBS-induced colitis [56], and suppression of inflammatory TNF signaling via modulation of PKA and ERK pathways [57]. Here, TNF is linked to colitis.