We investigated the impact of the interaction of LFA-1 on PBMCs and ICAM-1 on HK-2 cells on the EMT of HK-2 cells. HK-2 cells after stimulation of TGF-b 1 (0.1 ng/ml) for 24 hrs were co-cultured with PBMCs for a further 24 hrs (HK-2-TGF-b 1 (0.1)-PBMCs). Then, the changes of epithelial cell junction markers and mesenchymal markers on HK-2-TGF-b 1 (0.1)-PBMCs were investigated by real-time RT-PCR and western blotting analysis. HK-2 cells after stimulation of TGF-b 1 (0.1 ng/ml) without coculture with PBMCs (HK-2-TGF-b 1 (0.1)) and HK-2 cells without stimulation of TGF-b 1 co-cultured with PBMCs (HK-2-PBMCs) were investigated as control experiments. The results of real-time RT-PCR showed that the expression of epithelial cell junction markers (E-cadherin and occludin) further significantly decreased and that of mesenchymal markers (vimentin and fibronectin 1) further significantly increased in HK-2-TGF-b 1 (0.1)-PBMCs compared with those of controls. These EMT marker changes on HK-2-TGF-b 1 (0.1)-PBMCs were blocked by anti-LFA-1 mAb or anti-ICAM-1 mAb, whereas they were not blocked by isotype control mAb (Figure 4 ). Phase contrast microscopy analysis showed that HK-2-TGF-b 1 (0.1)-PBMCs changed more, morphologically, from a cobblestone-like monolayer to spindle-shaped fibroblast-like cells, than the controls. These morphological changes of HK-2-TGF-b 1 (0.1)-PBMCs were mitigated by anti-LFA-1 mAb or anti-ICAM-1 mAb, whereas they were not mitigated by isotype control mAb ( Figure The interaction of HK-2 cells pre-stimulated with TGF-b 1 and PBMCs up-regulated TGF-b 1 level in co-culture media To investigate whether pre-stimulation of HK-2 cells by TGFb 1 contributes to EMT or just induces the CXCL12 that activates LFA-1 on PBMCs, we employed a transwell co-culture system as described above. HK-2 cells without TGF-b 1 stimulation and PBMCs were co-cultured in a lower plate and HK-2 cells prestimulated by TGF-b 1 (10.0 ng/ml, 1.0 ng/ml and 0.1 ng/ml) were cultured in an upper insert. After 24 hrs of incubation, TGFb 1 concentrations in the media in the lower wells were determined by TGF-b 1 ELISA. The concentrations of TGF-b 1 in the coculture media of HK-2 cells and PBMCs in the lower wells were about threefold higher than those of HK-2 cells alone (Fig. 6 ).