Cell Biol Toxicol (2011) 27:69–81 Fig. 3 Immunocyto- chemistry of keratins. HaCaT cells were treated for 24, 48, and 72 h with sodium fluoride at low (0.5 mM) or high dose (5 mM) of NaF. Only the 24-h treatment pattern of expression is shown; similar profiles were obtained after 48 and 72 h. Monoclonal antibodies as in Fig. 2 were applied. C, non-treated cells. Nuclear staining with DAPI was included to show cell density from all cover slips. The expression of K1/10 and K15 was decreased after low dose and high dose treatment, whereas K13 and K19 expression remained unchanged. Note the pattern of expression of K1/10 and K15: positive cells occur in clusters. Expression of K15 and K1/ 10 decreased substantially at high dose NaF 75