OBJECTIVE To evaluate the immunological characteristics of an immunonanoparticles targeting to human lens epithelial cells and to study if it could internalize into and inhibit the proliferation of target cells in vitro. METHODS Crosslinker carbodiimide was used to couple McAb HILE6 (anti-lens epithelial cells antibody) with 5-fluourouracil-loaded polyactic acid nanoparticles PLA (5-FU)-NP to prepare the immunonanoparticles HILE6-PLA (5-FU)-NP. The molar ratio of HILE6 and 5-FU in the immunonanoparticles were observed. The immunological activity of the antibodies in the immunonanoparticles was assessed by ELISA. The third passage lens epithelial cells were divided into four groups; immunonanoparticles, 5-FU nanoparticles, mixed HILE6 and 5-FU nanoparticles and the controls. The proliferation of lens epithelial cells were evaluated by MTT analysis. Internalization of immunonanoparticles, 5-FU nanoparticles and McAb HILE6 were observed by indirect immunofluorescence study of lens epithelial cells. RESULTS The molar ratio of 5-FU to HILE6 in the immunonanoparticles was 1809:1 and 84% of the original immunological activity of antibodies could be retained. The immunonanoparticles inhibited the proliferation of lens epithelial cells, which was significantly greater than original 5-FU nanoparticles or the blend group. The IC(50) inhibition of immunonanoparticles was 5.0 microg/ml 2 hours after treatment. The immunonanoparticles were bound to the cells surface in 30 minutes; internalized in 2 hours and accumulated around the nucleus after 4 hours. CONCLUSIONS The immunonanoparticles retain immunological activity and could specifically internalize into the lens epithelial cells to inhibit their proliferation.