P210 bcr/abl is expressed in tissues involved in the myeloproliferative process. Cells (5 × 10⁶) were loaded per lane and detected with the 8E9 abl-specific monoclonal antibody (Pharmingen). Many of the lower molecular weight bands are most likely the result of proteolysis due to the high percentage of neutrophils in the cell lysates.28 Lanes 1 through 4, bone marrow, peripheral blood, spleen, and liver cells from a Mig210 mouse. Lane 5, day-12 cells from bone marrow cultures transduced with Mig185. Mig185 is similar to Mig210, except Mig185 expresses P185 bcr/abl (Miller and Pear, unpublished data). Lane 6, Balb/c bone marrow cells. The band at approximately 140 kD in all lanes is c-abl. Arrows indicate the 210- and 185-kD proteins.