Significance Of MHC Expression And Immunological Mechanism In Idiopathic Inflammatory Myopathy

Idiopathic inflammatory myopathies (IIM) are a group of acquired autoimmune diseases, whose etiology is still unknown. IIM include three subtypes: PM (polymyositis), DM (dermatomyositis) and sIBM (sporadic inclusion body myositis). In 2003, new diagnostic criteria was introduced by Dalakas MC for IIM in which the CD8/MHC-â… c omplex is considered a specific immunopathological marker and MHC classâ… widely express was used as diagnostic evidence for PM, which further established an important status for molecule immunopathological methods. Major histocompatibility complex (MHC) which consists of three classes, is a group of genes markedly polymorphism in mammal. MHC classâ… andâ…¡molecules are involved in antigen-presenting, mediating endogenous and exogenous immunoreactions. According to many results about the expression of MHC classâ… molecules in IIM, we could conclude: 1. MHC classâ… molecule widely express on the sarcolemma in PM, while in DM the molecule showed intensely positively express on skeletal muscle fibers in the perifascicular area, and both in PM and DM the molecule express independently of inflammatory infiltrates; 2. MHC class â… molecule up-regulated expression in the early stage of DM and PM when no inflammatory cells infiltrate, indicating that maybe the molecule participated and motivated pathologic change in myositis; 3. Using corticosteroids and/or immunosuppressive agent treatment shortly has a remarkable effect on the positive expression of MHC classâ… molecule on fibers in DM and PM; 4. MHC classâ…¡molecule showed the significance of differential diagnosis between IIM and other neuromuscular diseases which are similar to IIM in clinical manifestation and pathologic appearance, showing inflammatory cells infiltration. In IIM MHC classâ…¡molecule positively express on the fibers, while in other neuromuscular diseases negatively express. Anti-MHC classâ… molecule, CD8 molecule monoclonal antibody immunohistochemistry stains pathological analysis on the basis of skeletal muscle biopsy histochemical stains show considerable significance for the typing diagnosis and differential diagnosis between IIM and other myopathies.