A monoclonal antibody elicited to human platelet monoamine oxidase. Isolation and specificity for human monoamine oxidase B but not A.

We have isolated a mouse monoclonal antibody to human platelet monoamine oxidase (MAO) B. The antibody (MAO-1C2) was isolated from a fusion of mouse myeloma P3/X63 Ag8 to spleen cells from a BALB/c mouse immunized with a partially purified platelet preparation in which an estimated 21-31% of the protein was [3H]pargyline-labeled MAO B. The antibody indirectly immunoprecipitates both [3H]pargyline-labeled, catalytically inactive human MAO B, and unlabeled, catalytically active human MAO B. Binding of the antibody to MAO B has no detectable effect on catalytic activity. MAO-1C2 is specific for human MAO B, and fails to immunoprecipitate MAO A indirectly from human placenta or liver. Its ability to immunoprecipitate human MAO B but not MAO A from extracts of human liver provides a convenient technique for separating the two forms of the enzyme for comparative studies. The antibody does not recognize mouse liver MAO B, suggesting that the determinant is not universally expressed on MAO B from all species.