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Expression of medial class I histocompatibility antigens on RMA-S mutant cells
E Hermel1, E Grigorenko, K F Lindahl
1Howard Hughes Medical Institute, Department of Microbiology, University of Texas Southwestern Medical Center, Dallas 75235-9050.
Abstract:
The RMA-S mutant T cell line is defective in H-2b restricted antigen presentation and has markedly reduced surface expression of Kb and Db. We examined RMA-S for the expression of the medial class I histocompatibility antigens Qa1b and Mta. While RMA-S targets varied in their susceptibility to lysis by cytotoxic T lymphocytes (CTL) specific for Qa1b, Mta levels were detectable but consistently low compared to the parent RMA cell line. Addition of synthetic ND1 alpha 1-26 or ND1 alpha 1-17 peptides that mimic MTF alpha (the ligand of Mta) increased killing of RMA-S by anti-Mta alpha CTL to levels comparable to or better than RMA, with 300 nM peptide being fully effective. None of the MTF peptides increased the killing of RMA-S by anti-H-2b or anti-Qa1b CTL, even at the highest (1 microM) peptide concentrations. RMA-S cells treated with 100 microM of either the ND1 alpha 4-26 or ND1 alpha 1-26 peptides showed a small increase in the fluorescent staining for beta 2-microglobulin but not for H-2Kb or H-2Db. These results show that Mta and Qa1b, although affected, are not obliterated by the defect in RMA-S cells; that the association of MTF peptides with HMT is exclusive; and that MTF enters the endoplasmic reticulum in the same fashion as other endogenous peptides.
Insights
The RMA-S mutant T cell line shows reduced expression of key immune molecules. Supplementing with specific peptides restored antigen presentation, indicating MTF peptides associate exclusively with HMT and enter the endoplasmic reticulum.
Area of Science:
- Immunology
- Molecular Biology
- Cellular Biology
Background:
- The RMA-S mutant T cell line exhibits defects in H-2b restricted antigen presentation.
- Surface expression of H-2Kb and H-2Db is significantly reduced in RMA-S cells.
- Medial class I histocompatibility antigens Qa1b and Mta expression were investigated in RMA-S cells.
Purpose of the Study:
- To investigate the expression of Qa1b and Mta in the RMA-S mutant T cell line.
- To determine the effect of synthetic MTF peptides on antigen presentation in RMA-S cells.
- To elucidate the mechanism of MTF peptide association with HMT and ER entry.
Main Methods:
- Flow cytometry was used to assess surface expression of MHC class I molecules.
- Cytotoxic T lymphocyte (CTL) assays were performed to evaluate antigen presentation.
- Treatment with synthetic ND1 alpha peptides was employed to assess functional recovery.
Main Results:
- Mta levels were low in RMA-S cells compared to parent RMA cells, while Qa1b susceptibility varied.
- Synthetic MTF peptides (ND1 alpha 1-26, ND1 alpha 1-17) restored anti-Mta alpha CTL killing of RMA-S cells.
- MTF peptides did not enhance killing by anti-H-2b or anti-Qa1b CTL, and did not increase H-2Kb/Db surface expression.
Conclusions:
- Mta and Qa1b expression are affected but not abolished in RMA-S cells.
- The association of MTF peptides with HMT is exclusive.
- MTF peptides enter the endoplasmic reticulum similarly to other endogenous peptides.