A case of B-CLL expressing P-glycoprotein in peripheral leukocytes. Methodological considerations

P-glycoprotein, the molecular marker of multidrug resistance, was investigated by means of the specific monoclonal antibody C219 in circulating lymphocytes obtained from a patient affected by B-CLL, who had undergone chemotherapy with chlorambucil and CVP. Dot-immunobinding and immunoblotting revealed the presence of P-glycoprotein in the cell lysate, but the immunoperoxidase method and indirect immunofluorescence carried out with a fluorescence microscope and a cytofluorimeter failed to detect the protein. Some methodologic problems are discussed.