Membrane dynamics of HL-A-anti-HL-A complexes of human normal and leukaemic lymphocytes.

Membrane dynamics of human lymphocytes treated with anti-HL-A antibodies were studied by means of indirect membrane fluorescence. When cells were incubated at 37°C for several hours, a striking diminution of the labelling index was observed. Furthermore, the pattern of the membrane fluorescence changed from a ring-shaped or patchy fluorescence to a polar concentration of the label (cap formation'). Cap formation' could be inhibited by incubation at 0°C and by 3 × 10 M sodium azide. Part of the labelled HL-A–anti-HL-A complexes could be detected within intracellular vesicles, which suggests uptake by endocytosis. Lymphocytes of patients with chronic lymphocytic leukaemia (CLL) did not show a decrease of the labelling index. `Cap formation' was almost completely lacking, and uptake of HL-A–anti-HL-A complexes by endocytosis was not observed. These findings indicate an impairment of membrane dynamics of CLL lymphocytes. The importance of these membrane dynamics for the activation of lymphocytes is discussed.