Application of the avidin-biotin-peroxidase complex technique for ultraimmunocytochemical characterization of leukemic cells

Syndecan-1/CD138 expression in normal myeloid, acute lymphoblastic and myeloblastic leukemia cells

Stabilization of cell surface antigens and preservation of ultrastructural integrity are important aspects of immunoelectron microscopical studies. In the present study, 4 anti-syndecan-1/CD138 (B-B2, B-B4, MI15, 1D4) monoclonal antibodies (mAbs) were applied in combination with periodatelysine-paraformaldehyde (PLP) fixation and indirect pre-embedding peroxidase electron microscopical immunocytochemistry to analyse the localization and function of these molecules in normal myeloid cells, acute lymphoblastic leukemia (ALL) cells and acute myeloblastic leukemia (AML) cells. One case of normal human bone marrow, 3 cases of untreated AML and 2 cases of untreated ALL were studied. Samples were immediately fixed for 4 h in freshly-prepared PLP fixative in 0.037 mol/L phosphate buffer, pH 7.4, containing 10 mmol/L sodium metaperiodate, 75 mmol/L lysine, and 2% paraformaldehyde. Expression of syndecan-1 was found at the plasma membrane of all cell types. Staining intensity at the membrane of AML cells was stronger than that on the membrane of normal myeloid and ALL cells. We conclude that anti-syndecan-1/CD138 mAbs in combination with the method described here are a suitable tool for detection of cell surface syndecan molecules in cells originating from progenitor cells that can differentiate in both myeloid and lymphoid cells.