Expression and characterization of recombinant soluble peptide: I-A complexes associated with murine experimental autoimmune diseases

Radu, Caius G., Ober, Bertram T., Colantonio, Lucia, Qadri, Ayub and Ward, E. Sally (1998) Expression and characterization of recombinant soluble peptide: I-A complexes associated with murine experimental autoimmune diseases. Journal of Immunology, 160 (12), 5915-5921.

Abstract

Structural and functional studies of murine MHC class II I-A molecules have been limited by the low yield and instability of soluble, recombinant heterodimers. In the murine autoimmune disease experimental autoimmune encephalomyelitis and collagen-induced arthritis, MHC class II molecules I- A(u) and I-A(q) present peptides derived from myelin basic protein and type II collagen, respectively, to autoreactive T cells. To date, systems for the expression of these two I-A molecules in soluble form for use in structure- function relationship studies have not been reported. In the present study, we have expressed functional I-A(u) and I-A(q) molecules using a baculovirus insect cell system. The chain pairing and stability of the molecules were increased by covalently linking the antigenic peptides to β-chains and adding carboxyl-terminal leucine zippers. Peptide:I-A(q) complex quantitatively formed an SDS-stable dimer, whereas peptide:I-A(u) formed undetectable amounts. However, the two complexes did not show any significant difference in their response to thermal denaturation as assessed by circular dichroism analyses. The autoantigen peptide:I-A complexes were highly active in stimulating cognate T cells to secrete IL-2 and inducing Ag-specific apoptosis of the T cells. Interestingly, the T cells were stimulated by these soluble molecules in the apparent absence of experimentally induced cross- linking of TCRs, indicating that they may have therapeutic potential in autoimmune disease models.

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Contributors

Author: E. Sally Ward

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