Cap formation

When molecules on the surface of a cell are crosslinked, they are moved to one end of the cell to form a “cap”. This phenomenon, the process of which is called cap formation, was discovered in 1971 on lymphocytes and is a property of amoebae and all locomotory animal cells except sperm. The crosslinking is most easily achieved using a polyvalent antibody to a surface antigen on the cell. Cap formation can be visualised by attaching a fluorophore, such as fluorescein, to the antibody.