Cytotoxic T lymphocytes and antibodies after orthotropic penetrating keratoplasty in rats treated with dichloromethylene diphosphonate encapsulated liposomes

Abstract

PURPOSE. To investigate the immunological basis for the prolonged corneal allograft survival after subconjunctival injections of liposomes filled with dichloromethylene diphosphonate (Cl 2 MDP-LIP). METHODS. F344 rats received orthotropic DA corneal grafts. One group of rats was treated with subconjunctival injections of Cl 2 MDP-LIP on days 0, 2, 4, 6 and 8 postoperatively, the control groups received no treatment. Nineteen or 42 days postoperatively cytotoxic T lymphocyte (CTL) activity was measured in the lymph nodes draining the grafted and the contralateral eyes, in the spleen and the mesenteric lymph nodes. Sera taken at the same time points were tested for presence of lytic alloantibodies. RESULTS. On day 19 CTL activity in submandibular lymph nodes draining the grafted eyes was similar in the 2 groups. In the mesenteric lymph nodes high CTL activity was found in the untreated rats and low in the Cl 2 MDP-LIP rats. The spleen showed high CTL activity in the untreated group but no activity in the liposome group. Forty two days postoperatively a decline in CTL activity was seen in both groups. Complement dependent anti-donor antibodies were absent in the Cl 2 MDP-LIP group at both time points whereas antibodies were present on days 19 and 42 in the untreated group. CONCLUSIONS. Repeated subconjunctival injection of Cl 2 MDP-LIP restricts the induction of cellular cytotoxicity against donor antigens to the regional lymph nodes and suppresses cytotoxic antibody formation.