Abstract: To study the role of immune mechanism in the pathogenesis of idiopathic portal hypertension（IPH）. Methods： Subgroups of T and B lymphcyte were assyed by flow cytometric method.Serum levels of Soluble tumor necrosis factorα receptor II (sTNF rII) and soluble vascular cell adhesion molecule1 (sVCAM1) in IPH, normal and cirrhosis group were measured by ELISA method. And the expression of VCAM1 in liver were determined in IPH, cirrhosis and normal patients. Results： The prevalence of CD3+,　CD4+ and CD8+ in peripheral blood were significantly lower in the IPHs than in the healthy controls (P＜0.05),　the ratio of CD4+/CD8+ was much higher in the IPHs than in the controls (P＜0.05),　whereas there was no significant difference of CD19+ between the IPHs and the controls (P＞0.05). Expression of VCAM1 in the IPHs was found mainly in endothelial cells and sinusoidal lining cells around portal tracts,and scattered in sinusoidal lining cells in cirrhosis,　whereas was not found in normal group. Serum levels of sVCAM1 and sTNFα r II increased in the IPHs compared with those in the controls［(38.84±8.38)ng/ml vs 28.14±7.37ng/ml；（44.06±17.28）ng/ml vs (32.18±8.72)ng/ml,（P＜0.05）］. In addition, TNFα induced the up regulation of VCAM1(r=0.556, P＜0.05) in IPH. Conclusion

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