Objective: To investigate the influence of anti-keratin autoantibodies (AK auto Abs) on telom-erase activity of squamous cell carcinoma cultured in vitro and the mechanisms of the inhibitory effects of AK auto Abs on squamous cell carcinoma. Methods: Influence of AK auto Abs on the proliferation of Tca cells was observed by MTT colorimetry. Telomerase activity of cultured Tca cells and human keratinocytes was determined by telomeric repeat amplication protocol-ELISA (TRAP-ELISA) and polyacrylamide gel elec-trophoresis (PAGE). After being treated with AK auto Abs for 36 h at a concentration of 4, 8, 16 mg/L respectively, the changes of telomerase activity of Tea cells were also detected by TRAP-ELISA and PAGE. Results: MTT colorimetric determination showed that the capacity of proliferation of Tca cells correlated negatively with the concentration of AK auto Abs (r= -0. 74, P<0. 01). TRAP-ELISA and PAGE showed that telomerase activity of Tca cells increased significantly compared to that of cultured human Objective: To investigate the influence of anti-keratin autoantibodies (AK auto Abs) on telom-erase activity of squamous cell carcinoma cultured in vitro and the mechanisms of the inhibitory effects of AK auto Abs on squamous cell carcinoma. Methods: Influence of AK auto Ties of the proliferation of Tca cells was observed by MTT colorimetry. Telomerase activity of cultured Tca cells and human keratinocytes was determined by telomeric repeat amplication protocol-ELISA (TRAP-ELISA) and polyacrylamide gel elec-trophoresis (PAGE). After being treated with AK auto Abs for 36 h at a concentration of 4, 8, 16 mg/L respectively, the changes of telomerase activity of Tea cells were also detected by TRAP-ELISA and PAGE. Results: MTT colorimetric determination showed that the capacity of proliferation of Tca cells correlated negatively with the concentration of AK auto Abs (r= -0.74, P<0. 01). TRAP-ELISA and PAGE showed that telomerase activity of Tca cells increased significantly compared to tha t of cultured human