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Introduction of HLA-A/B antigens into lymphoid cell membranes by cell-liposome fusion.

Conditions were optimized for surface binding by mouse lymphblastoid cell lines of liposomes containing purified human histocompatibility antigens. Antigens were reconstituted into lipid vesicles by detergent dialysis, and were incubated with the acceptor cell lines. After washing, the amount of HLA antigen on the cell surface was quantitated by double antibody radioimmunoassay. Uptake and surface expression was shown to be dependent upon vesicle phospholipid composition, vesicle:cell ratio, acceptor cell line, and stage of cell growth. These studies indicate that by using vesicles composed of 50% phosphatidylethanolamine/50% phosphatidylserine it is possible to introduce into the mouse EL4 cell surface about 70% of the amount of HLA expressed normally on the human lymphoblastoid line JY. The antigen is stably expressed on the surface for several hours and appears to be integrated into the cell membrane, as assessed by both fluorescence microscopy and susceptibility to lysis by using anti-HLA antibody and complement. The method used has the advantage over previously described procedures of not requiring the use of fusogenic proteins or agents such as polyethylene glycol or lysophospholipids, which might perturb overall membrane structure or properties.