Specific uptake of alpha-fetoprotein by malignant human lymphoid cells.
We have studied the ability of human B- and T-lymphoblastoid cell lines, as well as of peripheral lymphoid cells from leukemia patients, to take up alpha-fetoprotein (AFP) and other serum proteins. Two technical approaches have been employed, both using fluorescent protein derivatives (FITC-proteins): microscopic examination of labelled cells using epifluorescent illumination and quantitation of endocytosed proteins by fluorescence-activated cell sorting (FACS). Compared to human resting T-lymphocytes, all T- and B-cell lines tested exhibited positive staining for fluoresceinated AFP and transferrin (Tf) and a significant increase, up to 100-fold, of the number of AFP and Tf molecules endocytosed per cell. Labelling was prevented or strongly diminished by a 100-fold excess of unlabelled protein. Preliminary results with peripheral lymphoid cells harvested from leukemia patients showed the presence of AFP- and Tf-positive cells in the blood of all patients examined. Intensity of labelling was related to the type of leukemia cells and/or the degree of cell maturation. Most cell lines exhibited positive staining for alpha 2-macroglobulin (alpha 2M) and also, to a lesser extent, for serum Vitamin D3 binding protein (DBP). In contrast, no labelling was observed with FITC-serum albumin (FITC-Alb) or FITC-ovalbumin (FITC-OVA). Comparative uptake of several FITC-proteins by a single cell population revealed significant quantitative and qualitative differences.
D001798:Blood Proteins / Q000378:metabolism; D002460:Cell Line; D005434:Flow Cytometry; D006801:Humans; D007938:Leukemia / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D011956:Receptors, Cell Surface / Q000032:analysis; D018000:Receptors, Peptide; D014168:Transferrin / Q000378:metabolism; D000509:alpha-Fetoproteins / Q000378:metabolism*
D001798:Blood Proteins; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; D014168:Transferrin; D000509:alpha-Fetoproteins; C042144:alpha-fetoprotein receptor, human