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TAP-independent, beta 2-microglobulin-dependent surface expression of functional mouse CD1.1
R R Brutkiewicz1, J R Bennink, J W Yewdell
1Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892-0440, USA.
Insights
Functional expression of mouse CD1.1 requires beta 2-microglobulin (beta 2m) but not the peptide transporter (TAP). This finding clarifies CD1 molecule cell surface expression and T cell recognition requirements.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- CD1 molecules are crucial for T cell recognition but their cell surface expression requirements are not fully understood.
- CD1 molecules comprise beta 2-microglobulin (beta 2m) and a non-MHC-encoded protein homologous to MHC class I alpha chains.
Purpose of the Study:
- To investigate the requirements for cell surface expression and T cell recognition of mouse CD1.1.
- To determine the role of beta 2m and the Transporter associated with Antigen Processing (TAP) in CD1.1 function.
Main Methods:
- Insertion of the mouse CD1.1 gene into vaccinia virus for recombinant expression.
- Infection of normal and mutant cell lines with recombinant vaccinia virus.
- Assessment of CD1.1 expression using a specific monoclonal antibody (3C11).
- T cell hybridoma (DN32.D3) assays measuring IL-2 production in response to thymocytes from normal and mutant mice.
Main Results:
- Mouse CD1.1 expression is dependent on beta 2m.
- Mouse CD1.1 expression is independent of the MHC-encoded peptide transporter (TAP).
- T cell hybridoma activation is dependent on beta 2m but not TAP.
Conclusions:
- Functional expression of mouse CD1.1 on the cell surface requires beta 2m.
- The peptide transporter (TAP) is not involved in the expression or function of mouse CD1.1.
- These findings elucidate key molecular requirements for CD1-mediated immune responses.
Abstract:
CD1 molecules consist of beta 2-microglobulin (beta 2m) noncovalently complexed to a non-major histocompatibility complex (MHC)-encoded monomorphic integral membrane protein homologous to MHC class I alpha chains. Little is known about the requirements for cell surface expression and T cell recognition of CD1. We inserted the mouse CD1.1 gene into vaccinia virus to create a recombinant virus expressing CD1.1 under the control of a viral promoter. Using this recombinant virus to infect normal or mutant cell lines, we found that the expression of molecules reactive with the CD1.1-specific monoclonal antibody 3C11 requires the expression of beta 2m but was not affected by the absence of the MHC-encoded peptide transporter (TAP). Consistent with these results, IL-2 production by the mCD1.1-specific T cell hybridoma DN32.D3 was induced by thymocytes from normal mice or mice with a homozygous deletion of the TAP1 gene, but not by thymocytes from mice with a homozygous deletion of the beta 2m gene. These results indicate that expression of functional mCD1.1 occurs in a beta 2m-dependent, TAP-independent manner.