Primary gingival keratinocytes were grown in organotypic (raft) cultures and treated with different concentrations of Zidovudine, beginning either at day 0 (Tissue Harvest A) or at day 8 (Tissue Harvest B). (Panels A, G, M, S, Y and EE) untreated rafts; (Panels B, H, N, T, Z, and FF) rafts treated with 0.5 µg/ml Zidovudine; (Panels C, I, O, U, AA, and GG) rafts treated with 1 µg/ml Zidovudine; (Panels D, J, P, V, BB and HH) rafts treated with 2 µg/ml, the cMax of Zidovudine; (Panels E, K, Q, W, CC, and II) rafts treated with 4 µg/ml Zidovudine; (Panels F, L, R, X, DD, and JJ) rafts treated with 6 µg/ml Zidovudine. Rafts were harvested at different points and stained with hematoxylin and eosin. DPT denotes days post treatment (Tissue Harvest B). Images are at 20 X original magnification.