Histological sections, prepared from control (CTL) mouse skin and mouse skin 1–5 days post NM, were stained with an antibody to phospho-H2A.X. Antibody binding was visualized using a Vectastain Elite ABC kit. One representative section from 3 mice/treatment group is shown (original magnification,× 400). E, epidermis; D, dermis; S, sebaceous gland; HF, hair follicle; asterisk, eschar. Black arrow, keratinocytes expressing phospho-H2A.X. Black arrowhead, inflammatory cell infiltrate. Left panels, mouse skin treated with NM; right panels, mouse skin treated with NM and 4338.