1. The selected polypeptide containing: α1 domain of the main histocompatibility complex (MHC) class II, where the polypeptide does not include the α2, β1 or β2 domain of MHC class II； or part of the α1 domain of MHC class II, where part of the α1 domain of MHC class II is able to bind to CD74 or reduce the expression or activity of CD74.2. The selected polypeptide according to claim 1, where the α1 domain contains the α1 domain of the MHC class II person, the α1 domain contains the domain DR-α1, DQ-α1, DP-α1, DM-α1 or DO-α1, the α1 domain contains amino acid residues 1-75 mature the MHC class II α chain or at least 5 consecutive amino acids thereof, the α1 domain contains the α1 domain of the α chain containing the amino acid sequence represented by any of SEQ ID NOS: 1-49, and / or the α1 portion of the MHC class II domain contains amino acid residues 38-58 of the mature DR-α chain or part thereof, or a region homologous to DPα or DQα. 3. The isolated polypeptide of claim 1, further comprising an antigenic determinant, wherein the antigenic determinant is covalently linked to the α1 domain, where the covalent bond contains a peptide linker or chemical crosslinking, and / or the antigenic determinant contains a myelin protein peptide antigen, a peptide antigen associated with an antigen associated with rheumatoid arthritis, a peptide antigen associated with uveitis, or a peptide antigen associated with type I diabetes. 4. The selected polypeptide according to claim 3, wherein the antigenic determinant is a myelin protein peptide antigen containing oligodendrocyte myelin glycoprotein peptide (MOG), myelin basic protein peptide (MBP) or proteolipid protein peptide (PLP), where the myelin protein peptide antigen contains MOG35-55, MBP85-99, MBP149-171 or PLP139-151, or antigenic determinant is a peptide antigen associated with type I diabetes, containing insulin B: 16-23.5. Stand out1. Выделенный полипептид, содержащий:α1 домен главного комплекса гистосовместимости (М
