Increased expression of cell adhesion molecules in inflammatory myopathies: diagnostic utility and pathogenetic insights

Context: Idiopathic inflammatory myopathies (IMs) have been postulated to be of autoimmune origin on the basis of expression of markers like MHC-1 and other mediators involved in autoimmunity such as cell adhesion molecules.

Aims: The present study aims to analyze the expression of cell adhesion molecules ICAM-1 and VCAM-1 and their respective ligands LFA-1 and VLA-4 in IMs, and to assess whether these markers, besides MHC-class 1 antigen and membrane attack complex (MAC), could be of any help in the diagnosis of these diseases.

Material and Methods: Retrospective analysis of 119 muscle biopsies consisting of 55 IMs (21 dermatomyositis, 31 polymyositis and 3 inclusion body myositis) and 64 controls received in our department from January 2004 to December 2005 was carried out immunohistochemically using monoclonal antibodies.

Statistical analysis: Chi square test and test for validity were used for analysis of differences in expression.

Results: Expression of ICAM and VCAM was significantly upregulated on blood vessels and muscle fibres in IMs as compared to controls, in which expression was weak or absent. LFA and VLA-4 were expressed in inflammatory cells in all inflammatory diseases in almost equal numbers.

Conclusions: IMs comprise 6% of all muscle diseases and IBM is not a common IM in India as reported in the Western literature. Our findings support the hypothesis of autoimmune origin of IMs. The difference between expression of these molecules in IMs and controls also has diagnostic implications and these markers should be included along with MHC-1 antigen and membrane attack complex (MAC) in the existing diagnostic armamentarium.