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Cultured human Langerhans cells resemble lymphoid dendritic cells in phenotype and function
Insights
Cultured human Langerhans cells (LC) transform into potent T-cell stimulators, resembling lymphoid dendritic cells. This suggests skin-resident human LC are immature precursors, similar to their murine counterparts.
Area of Science:
- Immunology
- Dermatology
- Cell Biology
Background:
- Freshly isolated human epidermal Langerhans cells (LC) are poor stimulators of T cells.
- Murine LC transform into potent stimulators upon culture, resembling lymphoid dendritic cells.
- This suggests resident LC may be immature dendritic cell precursors.
Purpose of the Study:
- To analyze the phenotype and morphology of human LC before and after culture.
- To assess the stimulatory capacity of cultured human LC.
- To compare human LC to murine LC and lymphoid dendritic cells.
Main Methods:
- Enzyme cytochemistry
- Monoclonal antibody panel (approx. 80 antibodies)
- Immunofluorescence microscopy and two-color flow cytometry
- Transmission electron microscopy
- Allogeneic mixed leukocyte reaction and oxidative mitogenesis assays
Main Results:
- Cultured human LC exhibited lymphoid dendritic cell morphology, phenotype, and function.
- LC became non-adherent, developed veils, decreased ATP/ADP'ase and non-specific esterase activity.
- Increased MHC class I and II expression, reduced FcII receptors, and appearance of CD40 marker.
- Cultured LC were potent T-cell stimulators.
Conclusions:
- Resident human LC, like murine LC, are immature precursors of dendritic cells.
- Cultured human LC differentiate into mature, lymphoid dendritic cell-like cells.
- These findings support the role of skin LC as precursors in lymph node immune responses.
Abstract:
Freshly isolated murine epidermal Langerhans cells (LC) are weak stimulators of resting T cells. Upon culture their phenotype changes, their stimulatory activity increases significantly, and they come to resemble lymphoid dendritic cells. Resident murine LC, therefore, might represent a reservoir of immature dendritic cells. We have now used enzyme cytochemistry, a panel of some 80 monoclonal antibodies, and immunofluorescence microscopy or two-color flow cytometry, as well as transmission electron microscopy, to analyse the phenotype and morphology of human LC before and after 2-4 d of bulk epidermal cell culture. In addition, LC were enriched from bulk epidermal cell cultures, and their stimulatory capacity was tested in the allogeneic mixed leukocyte reaction and the oxidative mitogenesis assay. Cultured human LC resembled human lymphoid dendritic cells in morphology, phenotype, and function. Specifically, LC became non-adherent upon culture and developed sheet-like processes (so-called "veils"), decreased their surface ATP/ADP'ase activity, and lost nonspecific esterase activity. As in the mouse, surface expression of MHC class I and II antigens increased significantly, and FcII receptors were significantly reduced. Markers that are expressed by dendritic cells (like CD40) appeared on LC following culture. Cultured human LC were potent T-cell stimulators. Our findings support the view that resident human LC, like murine LC, represent immature precursors of lymphoid dendritic cells in skin-draining lymph nodes.