Immunoprecipitation of Mpl-R protein. CMK cell extracts were immunoprecipitated with BAH-1 antibodies and subjected to SDS-PAGE followed by Western blotting using control MoAb or BAH-1 antibodies (A) or Mpl-R antibodies (B) as described in the Materials and Methods section. Arrow indicates the position of the c-Mpl. The reactive proteins were detected by using the ECL system (Amersham).