HLA-DM is expressed on the cell surface and colocalizes with HLA-DR and invariant chain in human Langerhans cells.
The subcellular distribution patterns of molecules involved in the process of antigen loading [HLA-DR, HLA-DM, and the cytoplasmic and luminal parts of the invariant chain (Ii, CD74)] were investigated in Langerhans cells (LC), both qualitatively and quantitatively. The analysis was performed by immunofluorescence labelling of acetone-fixed vertical cryostat sections from normal human skin specimens and subsequent examination using confocal laser scanning microscopy (CSLM). The intensity-modulated multiple-wavelength scanning (IMS) technique was used to enhance channel separation when scanning dual-labelled specimens. The mean (n = 9) relative epidermal volumes of reactivity were: HLA-DR 8%+/-3%, HLA-DM 6%+/-2%, luminal Ii 6%+/-2%, and cytoplasmic Ii 4%+/-1%. The difference between HLA-DR and the other epitopes was significant at the P<0.001 level. All molecule combinations, except the combination of HLA-DM and luminal Ii (which was not studied), were to various extents colocalized. Experiments performed on unfixed epidermal sheets showed that HLA-DM is present on the cell surface of LC, suggesting that HLA-DM may interact with HLA-DR on the surface to induce peptide loading.
Andersson
T
T
Department of Biomedical Physics, Royal Institute of Technology, Stockholm, Sweden.
Patwardhan
A
A
Emilson
A
A
Carlsson
K
K
Scheynius
A
A
D000328:Adult; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis*; D005260:Female; D005455:Fluorescent Antibody Technique; D006681:HLA-D Antigens / Q000032:analysis*; D006684:HLA-DR Antigens / Q000032:analysis*; D000949:Histocompatibility Antigens Class II / Q000032:analysis*; D006801:Humans; D007801:Langerhans Cells / Q000737:chemistry*; D018613:Microscopy, Confocal
D000944:Antigens, Differentiation, B-Lymphocyte; C416189:H2-M antigens; D006681:HLA-D Antigens; C084245:HLA-DM antigens; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; C045084:invariant chain