Intracytoplasmic immunofluorescence in multiple myeloma.

A new intracytoplasmic immunofluorescence staining procedure has been investigated to detect and quantify myeloma cells by means of flow cytometry. Freshly harvested bone marrow aspirations from 12 patients with multiple myeloma were treated with collagenase and Triton X-100, and incubated with different specimens of fluoro-isothiocyanate-marked antihuman immunoglobulins. DNA-staining was then done with propidium iodide. Biparametric evaluation in a cytofluorograph 6300A/FC 200 showed a characteristic cluster distribution of normal and pathological immunoglobulin-producing cells. This intracytoplasmic fluorochromic staining procedure may be significant for the specific identification of nonsecretive immunocytomas, which cannot be detected by serodiagnostic methods.