ACIDIFIED CHLOROQUINE TREATMENT FOR THE REMOVAL OF CLASS-I HLA ANTIGENS

With the aim of reducing the damage to platelets while effectively rem oving class I HLA antigens from their surfaces, we developed a new met hod using acidified chloroquine diphosphate. Platelets were treated wi th a 0.2 M solution of chloroquine diphosphate (pH 4.0). More than 90% of the platelets remained viable after treatment. While a marked redu ction in reactions of acidified chloroquine-treated platelets with mul tispecific HLA antisera was noted in comparison with phosphate-buffere d-saline-(PBS)-treated platelets, reactions with platelet-specific ant ibodies were preserved. This was demonstrated by immunofluorescence te sts and solid-phase and monoclonal antibody immobilization of platelet antigen assays. Aggregation responses, though reduced in comparison w ith PBS-treated platelets, were still preserved after acidified chloro quine treatment. Ultrastructural analysis did not show any significant difference from PBS-treated platelets. We conclude that treatment of platelets with acidified chloroquine diphosphate is a simple and effec tive method for removing class I HLA antigens from their surfaces with minimal damage to their structure and function.