Expression of the CD69 activation antigen on lymphocytes of patients with hip prosthesis

The aim of the study was to evaluate the sensitization to metals in patient s with Co-Cr hip prosthesis. Peripheral blood mononuclear cells (PBMC) were collected from 14 healthy donors and three groups of patients: 10 candidat es for primary total joint replacements, 11 patients with well-fixed implan t and 13 patients with aseptic loosening of the hip prosthesis. PBMCs were cultured with the metal ions employed for implant manufacturing and the exp ression of CD69 activation antigen on CD3/T lymphocytes was detected by flo w cytometry. Chromium extract increased significantly the expression of CD3 /CD69 phenotype in patients with loosening of hip prosthesis. The chromium- induced 'activation index' was higher in patients with loosening of hip pro sthesis than in healthy donors and in pre-implant patients. The cobalt-stim ulated PBMC of patients with either well-fixed or loosened prosthesis had a n 'activation index' significantly higher than healthy donors. The activati on index values were used to graduate the PBMC-response as 'normal' (greate r than or equal to 0.9 and < 2),'low' ( < 0.9) and 'high' (greater than or equal to 2): an high-activation index was observed only in chromium-exposed PBMC of patients with prosthesis. Our data show that chromium released fro m orthopedic implants could be responsible for the lymphocyte sensitization and flow cytometry is an easy and reliable method for monitoring the hyper sensitivity state in patients with metal prostheses. Activated lymphocytes in the peri-implant tissue are likely to elicit a localized immune response and contribute to maintain the inflammatory process evolving in the implan t failure. (C) 2000 Elsevier Science Ltd. All rights reserved.