The Drosophila position-specific antigens are a family of cell surface glycoprotein complexes.

Position-specific (PS)1 and PS2 monoclonal antibodies bind non-uniformly to the mature wing imaginal disc of Drosophila with respect to the boundary separating the dorsal and ventral developmental compartments. PS1 antibodies preferentially recognize dorsal cells, PS2 antibodies ventral cells. Antibodies of the two classes extract distinct sets of glycoproteins from an imaginal disc lysate. PS3 antibodies bind to both dorsal and ventral disc cells and extract both PS1 and PS2 glycoprotein sets together with an additional component. We show that the PS antigens are related multimeric glycoprotein complexes on the cell surface. PS3 antibodies recognize a glycoprotein present in all complexes, while PS1 and PS2 antibodies recognize unique components of their own complexes. Spatial and temporal correlations suggest the molecules may have a function in development.