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Distribution of HLA class II molecules in epidermal Langerhans cells in situ
A M Mommaas1, A A Mulder, C J Out
1Department of Dermatology, University Hospital Leiden, The Netherlands.
Insights
Langerhans cells (LC) show dynamic expression of HLA class II molecules. Isolation or activation redistributes and up-regulates these molecules on the cell surface, appearing in endosomal/lysosomal compartments.
Area of Science:
- Immunology
- Cell Biology
- Dermatology
Background:
- Langerhans cells (LC) are critical immune cells in the epidermis.
- Understanding HLA class II molecule expression in LC is vital for immune response studies.
Purpose of the Study:
- To investigate the expression patterns of HLA class II molecules in human Langerhans cells (LC).
- To determine the cellular localization and potential redistribution of HLA class II molecules upon LC isolation or activation.
Main Methods:
- Immunoelectron microscopy was employed to visualize HLA class II molecule expression.
- Double-labeling experiments utilized monoclonal antibodies against HLA class II and organelle markers (LAMP-1, CD63, alpha-glucosidase).
Main Results:
- In epidermis, HLA class II molecules were found on LC dendrites, forming a network, but not on the cell body.
- Isolated and activated LC exhibited uniform and strong HLA class II expression on their entire surface.
- HLA class II molecules were localized to intracellular vesicular structures, co-localizing with late endosome and early lysosome markers, but not Birbeck granules.
Conclusions:
- LC isolation and/or activation induces redistribution and up-regulation of surface HLA class II molecules.
- HLA class II molecules are expressed within endosomal/lysosomal compartments in human LC, suggesting a role in antigen processing.
Abstract:
We performed immunoelectron microscopic studies to investigate the expression of HLA class II molecules in Langerhans cells (LC). In the epidermis, LC expressed class II molecules on the plasma membrane of the dendrites, resulting in a class II positive reticulo-epithelial network, but not on the surface of the cell body. In contrast, isolated LC as well as activated LC in situ displayed an even and strong expression of class II molecules on their entire cell surface. Therefore, isolation and/or activation results in redistribution and up-regulation of class II molecules on the cell surface. In addition, double-labeling experiments were carried out with monoclonal antibodies to class II antigens and to LAMP-1, CD63 and alpha-glucosidase, specific markers for organelles of the endosomal/lysosomal system. The results show expression of class II molecules on intracellular, electron-dense vesicular structures, and co-localization of class II molecules and the markers for late endosomes and early lysosomes in human LC in situ. Expression of these markers was not found on Birbeck granules, an LC-specific organelle.