AIM: To evaluate the function of primary human corneal endothelial cells (HCEC) serving as immunological cells. METHODS: Expression of HLA-DP, -DQ, -DR, CD40, CD80, and CD86 was determined by immunohistochemical methods. Meanwhile, purified peripheral blood mononuclear cells(PBMC) were cocultured with primary HCEC which were pre-treated with and without γ -IFN respectively. The activation of lymphocytes was determined by FACS analysis. RESULTS: In coculture system, T lymphocyte was activated by primary HCEC, HLA-DP, -DQ, -DR and CD40 expression were increased by γ -IFN induction. Costimulatory molecular CD80 was shown on the endothelial cells. CONCLUSION: Primary HCEC are assumed to be involved in the corneal transplantation rejection process as potential antigen presenting cells (APC).