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Expression and function of Qa-2 major histocompatibility complex class I molecules in transgenic mice
A L Mellor1, P D Tomlinson, J Antoniou
1Division of Molecular Immunology, National Institute of Medical Research, Mill Hill, London, UK.
International Immunology
|May 1, 1991
Summary
Qa-2 molecules, encoded by major histocompatibility complex class I genes, can act as potent transplantation antigens. Transgenic expression in mice leads to rapid skin graft rejection and robust T-cell responses, similar to H-2 molecules.
Area of Science:
- Immunology
- Transplantation Biology
- Genetics
Background:
- Major histocompatibility complex (MHC) class I molecules play critical roles in immune responses and transplantation.
- Qa-2 molecules, encoded by MHC class I genes, have been considered weak transplantation antigens.
- Understanding the immunogenicity of Qa-2 molecules is crucial for transplantation research.
Purpose of the Study:
- To investigate the immunogenicity of Qa-2 molecules when expressed in transgenic mice.
- To determine if Qa-2 molecules can function as major transplantation antigens.
- To elucidate the role of Qa-2 molecule expression levels in T-cell responses.
Main Methods:
- Generation of transgenic CBA mice expressing Qa-2 molecules.
- Skin grafting experiments to assess rejection times.
- Analysis of Qa-2 specific cytotoxic T-cell responses.
- Comparison of Qa-2 molecules with different membrane anchoring mechanisms (glycophosphatidyl anchor vs. transmembrane domain).
Main Results:
- Transgenic expression of Qa-2 molecules induced rapid skin graft rejection and strong, Qa-2 specific, cytotoxic T-cell responses.
- Efficient rejection occurred regardless of whether Qa-2 molecules were anchored via a glycophosphatidyl anchor or a transmembrane domain.
- Rejection times were slightly longer for glycophosphatidyl-anchored Qa-2 molecules.
- These findings indicate Qa-2 molecules can function as major transplantation antigens, akin to H-2 molecules.
- Low expression levels of Qa-2 in non-transgenic mouse keratinocytes likely explain the weaker T-cell responses observed previously.
Conclusions:
- Qa-2 molecules can behave as major transplantation antigens when expressed at sufficient levels.
- The mechanism of membrane attachment influences rejection kinetics but not overall immunogenicity.
- Increased Qa-2 expression in transgenic mice significantly enhances its role in immune rejection and T-cell activation.