Fig. 2. Dose-response effect of TGF-ß1 on the proliferation and expansion of keratinocytes. (A) Long-term cultures were initiated with keratinocytes of the Adh⁺⁺⁺ or Adh^-/+ populations, and maintained with or without addition of exogenous TGF-ß1 at a concentration of 10, 30, 100 or 300 pg/ml throughout the culture period, as specified. Results are expressed as a cumulated cell output. (B) Long-term cultures were initiated with sorted keratinocytes of the Adh⁺⁺⁺EGF-R^-/+ subpopulation, and maintained in the presence or absence of exogenous TGF-ß1 at a concentration of 10 or 100 pg/ml throughout the culture period. Results are expressed as a cumulated cell output. Data represent means±s.d. of four replicate cultures from one typical experiment. (C) Long-term cultures were initiated with sorted keratinocytes of the Adh⁺⁺⁺EGF-R^-/+ subpopulation and maintained in the presence or absence of TGF-ß1 at the concentration that promotes self-renewal of immature keratinocytes (10 pg/ml). Typical morphology of the cells obtained in these two conditions after 85 and 95 days of culture is illustrated in Fig. 2C.