Major histocompatibility complex class I and II expression in idiopathic inflammatory myopathy.
BACKGROUND
We sought to study the intensity and pattern of major histocompatibility complex (MHC) I and II expression in muscle from patients with biopsy-proven idiopathic inflammatory myositis (IIM) including the subgroups, polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM).


METHODS
A total of 120 muscle biopsies (61 PM, 14 DM, and 45 IBM) were immunostained for MHC I and II. Staining was graded as follows. 0: no staining, 1+: ≤10% fibers, 2+: 10% to 25%, 3+: 25% to 50%, 4+: 50% to 99%, and 5+ 100%.


RESULTS
All IIM biopsies showed MHC I positivity; 93% showed MHC II positivity. The proportion of patients with MHC II score ≥3+ was higher in IBM than DM or PM. In DM, MHC I expression showed a perifascicular pattern. All IBM biopsies were immunopositive for MHC I and II; 30/45 were scored 5+.


CONCLUSIONS
Immunostaining for MHC I and II is a useful adjunctive test in diagnosis and subclassification of IIM.
*Department of Rheumatology, North Manchester General Hospital, Pennine Acute Hospital NHS Trust, Manchester, UK †Department of Neuropathology, Hanson Institute, Institute of Medical and Veterinary Sciences, Adelaide ‡Department of Rheumatology, Royal Adelaide Hospital §Department of Medicine Adelaide University, Adelaide, Australia.
Leena
L
Das
Peter C
PC
Blumbergs
Jim
J
Manavis
Vidya S
VS
Limaye
D015415:Biomarkers / Q000378:metabolism; D001706:Biopsy; D003882:Dermatomyositis / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D015870:Gene Expression; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009220:Myositis / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D018979:Myositis, Inclusion Body / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D017285:Polymyositis / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology
D015415:Biomarkers; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II