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Intercellular transfer of a soluble viral superantigen
1Wadsworth Center, New York State Department of Health, Albany, New York 12201-2002, USA.
Journal of Virology
|August 23, 2000
Summary
Mouse mammary tumor virus (MMTV) superantigens (vSAgs) can transfer between cells, allowing antigen-presenting cells (APCs) to present them to T cells. This intercellular transfer and subsequent processing are key for T-cell activation.
Area of Science:
- Immunology
- Virology
- Molecular Biology
Background:
- Mouse mammary tumor virus (MMTV) superantigens (vSAgs) are known to interact with T cells.
- Intercellular transfer of antigens can influence immune responses.
Purpose of the Study:
- To investigate the mechanism and requirements for intercellular transfer of MMTV vSAgs.
- To determine if vSAg transfer precedes viral infection and T-cell activation.
Main Methods:
- Experiments using Chinese hamster ovary (CHO) cells expressing vSAg.
- Utilizing fixed and unfixed antigen-presenting cells (APCs) including B-cell lymphoma and mouse splenocytes.
- Employing class II-negative, furin protease-deficient CHO variants (FD11).
- Analysis of cell-free supernatant for vSAg activity.
Main Results:
- vSAgs were readily transferred to MHC class II proteins on APCs.
- Intercellular transfer of vSAg, not MHC class II, occurred at the cell surface.
- Proteolytic processing of vSAg was essential for presentation.
- Soluble, processed vSAg in cell-free supernatant was sufficient for T-cell stimulation.
Conclusions:
- vSAgs can be intercellularly transferred and processed by APCs, independent of viral infection.
- Proteolytic cleavage is a prerequisite for vSAg activity, generating a soluble, active moiety.
- This mechanism may facilitate T-cell activation prior to or during MMTV infection.