The effect of cultivation and interferon treatment on the surface morphology of hairy cell leukemia cells

The ability of interferon to induce alterations in the surface morphology of malignant B cells from 4 patients with hairy cell leukemia (HCL) was investigated under scanning electron microscopy. Peripheral blood hairy cells showed the same surface features as those isolated from spleens involved with HCL, and constantly exhibited both ruffles and microvilli. Cultured hairy cells displayed extreme polarization of their surface microprojections, and very active surfaces with elongated microvilli and broad-based ruffles were evident. All 4 cases of HCL were treated with recombinant human leukocyte interferon in vitro, and one-third of the HCs from 3 cases displayed deformed surfaces with "bubbling" membrane and altered microprojections. Most of these IFN-treated hairy cells appeared to be larger in size compared to the untreated control cells, and frequently showed a villous bud-like formation at their extremity. The possibility that these unique surface alterations reflect IFN-induced changes in the cytoskeletal proteins and/or membrane components is discussed in light of the clinical efficacy of in vivo IFN treatment in HCL.