Signs of inflammation in both symptomatic and asymptomatic muscles from patients with polymyositis and dermatomyositis

Christina Dorph ^1*, Pernilla Englund ¹, Inger Nennesmo ² and Ingrid E Lundberg ¹

¹ Rheumatology Unit, Department of Medicine at Karolinska University Hospital, Sweden
² Department of Laboratory Medicine, Division of Pathology at Karolinska University Hospital, Sweden

^* To whom correspondence should be addressed. E-mail: christina.dorph{at}karolinska.se.

Accepted 26 June 2006

Abstract

Objectives: To determine whether muscle weakness is correlated to inflammation, expression of interleukin- 1 (IL-1) and major histocompatibility complex (MHC) class I and II expression on muscle fibres.

Methods: Muscle biopsies from clinically symptomatic (proximal muscles) and asymptomatic muscle (all distal but two proximal) in eight patients with polymyositis (PM) and three patients with dermatomyositis (DM) and from six healthy controls were analyzed by immunohistochemistry for presence of T cells, macrophages, IL-1 and MHC class I and II expression. Results were evaluated by conventional light microscopy and by computerized image analysis.

Results: Inflammatory infiltrates with T cells and macrophages were observed to an equal degree in both symptomatic and asymptomatic muscle. The numbers of capillaries with IL-1 expression were significantly higher in the symptomatic and asymptomatic muscle compared to healthy controls. The total IL-1& [alpha] expression per tissue section assessed by computerized image analysis was significantly higher in symptomatic muscles but not in asymptomatic muscles compared to controls. Neither the number of IL-1 positive capillaries nor the total IL-1 expression differed significantly between symptomatic and asymptomatic muscles. Expression of MHC classes I and II on muscle fibres was detected in both symptomatic and asymptomatic muscles but rarely in healthy individuals.

Conclusions: Inflammatory infiltrates, T cells, macrophages, MHC class I and II expression on muscle fibres as well as IL-1 expression were independent of clinical symptoms and were present to an equal degree in both proximal and distal muscles. Thus other factors seem to determine development of clinical symptoms. One such factor could be variations in physical demands.

Keywords: IL-1alpha, MHC class I, dermatomyositis, muscle biospy, polymyositis

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

• Korotkova, M, Helmers, S B., Loell, I, Alexanderson, H, Grundtman, C, Dorph, C, Lundberg, I E, Jakobsson, P-J (2008). Effects of immunosuppressive treatment on microsomal prostaglandin E synthase 1 and cyclooxygenases expression in muscle tissue of patients with polymyositis or dermatomyositis. Ann Rheum Dis 67: 1596-1602 [Abstract] [Full Text]  
• Tomasova Studynkova, J., Charvat, F., Jarosova, K., Vencovsky, J. (2007). The role of MRI in the assessment of polymyositis and dermatomyositis. Rheumatology (Oxford) 46: 1174-1179 [Abstract] [Full Text]