The nuclear autoimmune antigen Ku is also present on the cell surface.

Polyclonal antibodies were raised against the individual 85 and 70 kDa subunits of the Ku complex purified from nuclear extract prepared from the T cell line MLA144. They specifically recognise the appropriate subunits of the Ku complex from whole cell extract of HeLa cells using Western blot analysis. They are also able to identify the Ku proteins present in the cell membrane using FACS analysis.