Explore The Diagnostic Utility Of MHC Class â…  And CD4,CD8 Expression On The Muscle Biopsies From Patients With Idiopathic Inflammatory Myopathies

Objective:(1)To compare the clinical and pathological features of various subgroup of idiopathic inflammatory myopathies,so as to define the characteristic clinical and pathological features of each idiopathic inflammatory myopathy,namely PM,DM and IBM;(2)By means of immunohistochemistry and immunofluorescene methods to detect the expression of MHC-Ⅰ,CD4 and CD8 molecule in the idiopathic inflammatory myopathies;(3)To investigate the diagnostic utility of MHC classⅠin the various neuromuscular diseases and the differential diagnostic utility of CD8/MHC-Ⅰcomplex among the three distinct idiopathic inflammatory myopathies.Methods:This is a retrospective study carried out on 57 muscle biopsies from 57 patients that was performed at the neuromuscular institute of Qilu Hospital from September 2004 to August 2007.Of the 57 biopsies included,41 were ofⅡMs and 16 cases of other neuromuscular disease with inflammatory cells infiltration were taken as controls for comparison.We also select 10 cases with clinical signs of muscle weakness but with no positive findings on biopsies as normal control,which was validated as other systemic disorder finally.By means of immunohistochemistry and immunofluorescene methods to detect the expression of MHC-Ⅰ,CD4 and CD8 molecule in the idiopathic inflammatory myopathies.we also using immumofluorescene double label/stain method to detect the expression of CD8/MHC-Ⅰcomplex in the idiopathic inflammatory myopathies. Results:1.Results of expression of MHC-Ⅰ,CD4 and CD8 by means of irnmunoenzymochemistry methodMajor histocompatibility complex(MHC)classⅠexpression on the sarcolemma, which is absent in normal muscle fibers,is up-regulated in inflammatory myopathies. All the biopsies from DM(including the cases without inflammation)were positive for MHC classⅠ(100%positive rate)and the staining intensity was particularly strong in the perimysial region.Major histocompatibility complex classⅠpositivity was seen in 20(86.9%)of 23 PM cases and in 2(66.7%)of 3 IBM cases.The immnunoenzymochemistry study of CD4 and CD8 showed that the inflammatory cells infiltrated in DM were mostly CD4~+T cells,whereas in PM and IBM the infiltrated inflammatory cells were mainly CD8~+T cells,occasionally the phenomenon of CD8~+T cell invading into healthy muscle fiber can be seen. 2.Results of expression of MHC-Ⅰand CD8 molecule by means of immunofluorescene method(1)Results of expression of MHC-Ⅰby means of immunofluorescene method showed diffuse MHC-Ⅰexpression on sarcolemma,inflammatory cells and vascular endothelial cells in DM,and when compared to normal controls,the density of endomysial capillary decreased significantly.In PM and IBM,there are also diffuse MHC-Ⅰexpressions on the sarcolemma and endomysial infiltrated inflammatory cells.(2)Results of expression of CD8 molecule by means of immunofluorescene method:There are a large quantity of CD8~+T cells infiltrated into perimysium,mainly around the vessels.However,in PM and IBM,the infiltrated inflammatory cells mostly located at endomysium encircling the muscle fiber.3.Results of immunofluorescene double staining of CD8 and MHC-ⅠWe use the method of immunofluorescene double staining of CD8 and MHC-Ⅰto validate the existence of CD8/MHC-Ⅰcomplex inⅡMs.The results showed that there are no CD8/MHC-Ⅰcomplex was found in all.DM case,15(65.2%)in 23 PM cases and 1(33.3%)in 3 cases.Conclusions:1.Our study demonstrates that detection of MHC classⅠis of great utility in the diagnosis ofⅡMs—especially in DM—even in the cases that do not show inflammation.It is also of value in diagnosis of PM,but its positive rate is lower than DM(86.9%versus 100%).The result means the negativity of MHC-Ⅰdoes not rule out the possibility of PM,on the other hand it also suggest that the PM cases diagnoesd by the criteria proposed by Bohan and Peter may comprise other neuromuscular diseases which normally do not express MHC-Ⅰmolecule.Thus immunohistochemical detection of expression of MHC classⅠshould be included in the existing armamentarium in routine evaluation ofⅡMs,especially when there is uncertainty in diagnosis.It is useful to discriminate other close morphologic mimics, as MHC-Ⅰis not expressed in normal muscles and other neuromuscular diseases.If combined with the detection of CD4 and CD8 molecule,the diagnosis and differential diagnosis of the 3 distinctⅡMs subgroup would be better clarified,because the inflammatory cells infiltrated in DM were mostly CD4~+Tcells,whereas in PM and IBM the infiltrated inflammatory cells were mainly CD8~+Tcells.2.Although CD8/MHC-Ⅰcomplex(namely CD8~+Tcells invade non-necrotic muscle fiber expressing MHC-Ⅰon the sarcolemma)was believed to be the characteristic immunopathological feature,but our study also showed the positive ratio of CD8/MHC-Ⅰcomplex in PM was not very high,only 65.2%.This result demonstrates that CD8/MHC-Ⅰcomplex as the specific diagnostic marker of PM need to be further validated.