Abstract： Objective To observe the injurious effect of T cell activated by Staphylococcus enterotoxin B (SEB) on human pulmonary artery endothelial cell (HPAEC) and explore its possible mechanism. Methods HPAEC was cocultured with SEB-activated T cells supernatant, and the secretion of chemotactic factors from HPAEC was examined. The Transwell inserts was used in chemoattraction assays. After HPAECs were cocultured with T cells and 10 ng/ml SEB for 3 days, HPAEC damage was monitored by microscopy and the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Results Three kinds of tested chemokines showed a time-dependent increase in all supernatant of HPAEC incubated with different concentrations of T cells. After 72 hours, the monocyte chemoattractant protein-1 (MCP-1,ng/ml) in 1 × 10-2, 1 × 10-1 , 1× 100 T cell supernatant groups was 1. 240± 0. 103, 4. 200± 0. 305, 6. 500±0. 500, respectively, macrophage inflammatory protein-1a (MIP-1α, ng/ml) was 0. 210 ± 0. 015, 0. 287 ±0. 012, 0. 531 ± 0. 037, respectively, and Rantes (ng/ml) was 1. 420 ± 0. 074, 7. 634 ± 0. 630, 15. 700 ±1. 300, respectively. Rantes presented a two-phase secretion mode : in early 6 hours it increased swiftly, but relatively slow at 12, 24, 48, 72 hours. T cell adherent to polycarbonate membrane increased after SEB stimulation in superantigen group compared with control group without SEB stimulation (86. 38± 14. 50 vs.16. 50± 2. 50, P＜ 0. 01 ). When 10 ng/ml SEB activated T cell was cocultured with HPAEC, more of originally suspended cultured T cells adhered to HPAEC monolayer [(15. 50±1.08)% vs. (1.60±0. 22)%,P＜0.01], whereas the cell adhesion ratio decreased markedly in 1 μg/ml Met-Rantes group [(4. 39±0. 66)%, P ＜ 0. 01 ). FACs test of HPAEC-adherent T cell showed lymphocyte chemokine receptor 5 (CCR5)/CD4 and CCR5/CD8 increased over 2. 5 folds and 2.8 folds compared with 100 ng/ml SEB activated T cell. Cell death rate of HPAEC was increased when cocultured with SEB-activated T cell in superantigen group compared with HPAEC normal incubation group [(32. 50±4. 50)% vs. (3. 50±0. 50)%, P＜0. 01].Conclusion Increased chemoattraction and adherence of SEB-activated T cells to HPAEC could damage HPAEC; this effect was possibly due to up-regulation of CCR5 on T cell.