Acidified Chloroquine Treatment for the Removal of Class I HLA Antigens

With the aim of reducing the damage to platelets while effectively removing class I HLA antigens from their surfaces, we developed a new method using acidified chloroquine diphosphate. Platelets were treated with a 0.2 M solution of chloroquine diphosphate (pH 4.0). More than 90% of the platelets remained viable after treatment. While a marked reduction in reactions of acidified chloroquine‐treated platelets with multispecific HLA antisera was noted in comparison with phosphate‐buffered‐saline‐(PBS)‐treated platelets, reactions with platelet‐specific antibodies were preserved. This was demonstrated by immunofluorescence tests and solid‐phase and monoclonal antibody immobilization of platelet antigen assays. Aggregation responses, though reduced in comparison with PBS‐treated platelets, were still preserved after acidified chloroquine 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 effective method for removing class I HLA antigens from their surfaces with minimal damage to their structure and function. © 1993 S. Karger AG, Basel