Mononuclear cell-membrane "fluidity": a study in some haematological malignancies.

The polarization of fluorescence from diphenyl hexatriene embedded in the membranes of intact peripheral-blood mononuclear cells has been measured and used to assess the "microviscosity" or fluidity of the membrane. Cell preparations were examined from patients with various types of leukaemia and related conditions in which circulating primitive cells may occur. Significantly lower fluorescence polarization values were obtained in all samples from patients with chronic lymphocytic leukaemia, but normal results were obtained in cases of chronic granulocytic leukaemia, myelosclerosis, solid lymphomas and in acute leukaemias in remission. In relapsed acute leukaemia, fluorescence polarization indicated reduced "microviscosity" of the cell membrane when large numbers (greater than 10(9)/1) of primitive cells were present; normal "microviscosity" was indicated when less than 10(9)/1 primitive cells were present. However, exceptions occurred in both cases, and the technique failed to give warning of imminent relapse in one case. Our findings suggest that a reduction in "microviscosity" as indicated by this technique is not a general property of the blood leucocytes in all types of leukaemia, and that the technique cannot, at present, be regarded as an alternative method for detecting circulating primitive cells.