Soluble mhc complex and its usage

(57) Abstract: The present invention relates to the use of major histocompatibility complex (MHC) the new complex of molecules and such complexes. The present invention in one aspect, a class IIβ2 chain modifications, for example, basically including the full-length class IIβ2 chain deletions, regarding single chain MHC class II complexes. In another aspect, the invention comprises an immunoglobulin constant chain or fragment, wherein the single chain MHC class II. Moreover, polyspecific MHC complex is provided comprising at least one single-chain MHC class II molecules. MHC complexes of the invention: 1) T cell receptor antagonists and including peptide is a partial agonist, a screen in vitro for the identification and isolation of peptides that modulate activity of selected T cells, and 2 ) are useful for a variety of applications, including methods, for inhibiting or inducing an immune response in a mammal.