Cytoplasmic IgM in leukemic B cells by flow cytometry.
The presence of intracellular cytoplasmic immunoglobulin M (IgM) in leukemic cells from patients with acute lymphocytic leukemia (ALL) and chronic lymphocytic leukemia (CLL) was investigated by flow cytometry. The objective of the study was to develop a reproducible flow cytometric method. A Burkitt's lymphoma-derived B-cell line, Daudi, and a pre-B ALL, Nalm-6, served as prototypes. Normal B cells and cells from patients with chronic myelogenous leukemia (CML) were used as negative controls. Cytoplasmic mu was expressed in 77.3 +/- 7.5% (n = 10) of Nalm-6 cells. CALLA+ ALL and CML cells lacked cytoplasmic mu. The surface-membrane immunoglobulin on the viable B cells was blocked with purified goat anti-human IgM. Subsequently, the B cells were fixed in cold absolute methanol and stained with a fluorescein-conjugated goat anti-human IgM to demonstrate cytoplasmic IgM. After the surface-membrane IgM was blocked, normal B cells had no cytoplasmic IgM (0.3-0.5% positive cells) detectable by flow cytometry. However, the peripheral blood lymphocytes from five patients with CLL and the Daudi cells contained cytoplasmic IgM, ranging from 7.8 to 76.7% and 45.7 to 89.3%, respectively. We conclude that cytoplasmic mu in Nalm-6, CLL, and Daudi cells can be easily and rapidly demonstrated by flow cytometry.
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D003593:Cytoplasm / Q000276:immunology*; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins; D006041:Goats; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis*; D007938:Leukemia / Q000276:immunology*; D007945:Leukemia, Lymphoid / Q000276:immunology; D011817:Rabbits; D013861:Thiocyanates
D005452:Fluoresceins; D007075:Immunoglobulin M; D013861:Thiocyanates; D016650:Fluorescein-5-isothiocyanate