NGF and sarcoma: These strains may inhibit LPS-induced pro-inflammatory cytokines in the infant gut [164], via increasing indole-3-lactic acid (ILA) production, a tryptophan metabolite, which functions as a ligand of the aryl hydrocarbon receptor (AhR) by enhancing nerve growth factor (NGF) induction in pheochromocytoma (PC12) cells through the rat sarcoma/extracellular signal-regulated kinase (Ras/ERK) signalling pathway [165].