title: Characterization of intracellular HLA-DR, DM and DO profile in K562 and HL-60 leukemic cells.
abstract: Surface class-II antigen expression fires-up the antigen presentation process and development of immune response. The absence of surface HLA-DR is used in various systems to avoid immune recognition. Most leukemic cells use such mechanism to escape immune surveillance. Here, K562 and HL-60 leukemic cells were examined as to intracellular HLA-DR, -DM and -DO expression, if any. Immunofluorescence scored by UV-microscopy, flow cytometry or confocal microscope analysis detected intracellular pools of HLA-DR, -DO and to a lesser degree HLA-DM, whereas sub-cellular fractionation localized these molecules within endosomes. RT-PCR experiments revealed the presence of HLA-DRalphabeta, HLA-DMalphabeta and HLA-DObeta but not HLA-DOalpha transcripts. Despite the absence of the HLA-DOalpha chain, stable transfectants of K562 with a full length HLA-DObeta-EGFP construct showed that DObeta chain could be translocated to endosomes and form stable complexes with HLA-DR. Such complexes could be responsible for arresting HLA-DR molecules within endosomes, maintaining their surface class-II negative state.
authors.affiliation: Department of Biology, Laboratory of Immunology, University of Crete, Heraklion 714 09, Crete, Greece.
authors.forename: Lina
authors.initials: L
authors.lastname: Papadimitriou
authors.forename: Ioannis
authors.initials: I
authors.lastname: Morianos
authors.forename: Valentina
authors.initials: V
authors.lastname: Michailidou
authors.forename: Eva
authors.initials: E
authors.lastname: Dionyssopoulou
authors.forename: Simon
authors.initials: S
authors.lastname: Vassiliadis
authors.forename: Irene
authors.initials: I
authors.lastname: Athanassakis
mesh_terms: D011992:Endosomes / Q000378:metabolism; D018922:HL-60 Cells; D006681:HLA-D Antigens / Q000378:metabolism*; D006684:HLA-DR Antigens / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D007951:Leukemia, Myeloid; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D006681:HLA-D Antigens; C084245:HLA-DM antigens; C046148:HLA-DO antigens; D006684:HLA-DR Antigens