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Surface appearance and instability of empty H-2 class I molecules under physiological conditions
V Ortiz-Navarrete1, G J Hämmerling
1Institute of Immunology and Genetics, German Cancer Research Center, Heidelberg.
Summary
Empty major histocompatibility complex class I molecules appear on the cell surface of both mutant and normal cells. This suggests that peptide supply limits the surface expression of these critical immune molecules.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Major histocompatibility complex (MHC) class I molecules require antigenic peptides for cell surface assembly and expression.
- RMA-S mutant cells are believed to have defects in intracellular peptide loading, leading to absent surface MHC class I expression.
Purpose of the Study:
- To investigate the surface expression of MHC class I molecules in RMA-S mutant cells.
- To determine if "empty" MHC class I molecules are present on the cell surface and their stability.
Main Methods:
- Utilizing H-2 antibodies and rabbit antiserum to detect MHC class I molecules on RMA-S and wild-type RMA cells.
- Culturing RMA cells with a peptide to assess its effect on MHC class I conformation and surface presence.
Main Results:
- "Empty" MHC class I molecules were detected at the cell surface of RMA-S cells at 37°C.
- These empty MHC class I molecules rapidly denatured but remained cell-surface associated.
- Similar denatured MHC class I molecules were found on normal RMA cells, with reduced amounts after peptide loading.
Conclusions:
- Empty MHC class I molecules are expressed on the surface of both mutant and normal cells.
- The presence of empty MHC class I molecules on normal cells suggests that peptide availability is a limiting factor for their surface expression.