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Expression and function of B7 on human epidermal Langerhans cells
F W Symington1, W Brady, P S Linsley
1Seattle Biomedical Research Institute, WA 98199-1651.
Journal of Immunology (Baltimore, Md. : 1950)
|February 15, 1993
Summary
Human epidermal Langerhans cells (LCs) express B7 molecules upon culture, which are crucial for costimulating T cells. This finding clarifies the role of LCs as potent antigen-presenting cells (APCs) in T cell activation.
Area of Science:
- Immunology
- Cell Biology
- Dermatology
Background:
- Antigen-presenting cells (APCs) like Langerhans cells (LCs) are vital for T cell activation.
- B7 molecules on APCs provide essential costimulatory signals to T cells via CD28 and CTLA-4 receptors.
- B7 expression on human epidermal LCs, potent APCs, had not been previously characterized.
Purpose of the Study:
- To investigate the cell surface expression of B7 molecules on cultured and non-cultured human epidermal LCs.
- To determine the role of B7 expression in LC-mediated T cell proliferation.
- To elucidate the contribution of B7 and ICAM-1 to T cell responses against LCs.
Main Methods:
- Utilized a high-avidity CTLA4-Ig fusion protein to detect B7 expression on LCs.
- Employed flow cytometry with fluorescently labeled reagents for cell surface staining.
- Analyzed B7 gene expression via RT-PCR on epidermal cell mRNA.
- Assessed T cell proliferation using coculture assays with purified T cells and LCs, in the presence of blocking antibodies.
Main Results:
- Freshly isolated LCs did not exhibit detectable cell surface B7 expression.
- LCs cultured for one or more days showed specific B7 surface staining, localized to discrete foci.
- B7 gene expression was confirmed in both cultured and non-cultured epidermal cells.
- Both CTLA4-Ig and anti-CD54 (RR/1) antibodies inhibited T cell responses to LCs, with combined treatment yielding over 90% inhibition.
- CTLA4-Ig inhibited T cell stimulation by both fresh and cultured LCs, suggesting B7 expression is time-dependent in vitro.
Conclusions:
- B7 molecules are expressed on the cell surface of cultured human epidermal LCs.
- LC-expressed B7 plays a critical role in costimulating the proliferation of resting allogeneic CD4+ T cells.
- The findings highlight the importance of B7 in LC-mediated T cell activation and suggest that in vitro culture enhances LC's allostimulatory capacity through B7 upregulation.