AHR and Erythema: Next, we exposed HaCaT KC to 50 J/m2 and 200 J/m2 UVB (approximately equivalent to 0.25 and 1 minimal erythema dose for a fair-skinned individual [17]) and subsequently treated the cells with the AHR antagonist 3′-methoxy-4′-nitroflavone (MNF, 20 μM) to exclude putative UV-filtering effects.