The TH1 cells are derived from primary human renal proximal tubule epithelial cells （RPTECs） Immortalised by two lentiviral vectors carrying the human telomerase （hTERT） and the SV40 T antigen （Tag）.Both the hTERT and Tag genes in the lentiviral vectors are flanked by loxP sites. Transient Cre expression in TH1 cells leads to efficient proviral deletion and upregulation of some renal specific activities. Removal of the genes for cell immortalization also significantly decreases the rate of cell proliferation and ultimately leads to cell senescence, suggesting that the cell cycle control remains intact in TH1 cells despite continuous passage of these cells in culture.
