Myositis in mixed connective tissue disease: a unique syndrome characterized by immunohistopathologic elements of both polymyositis and dermatomyositis.
OBJECTIVE
To characterize the inflammatory cells, the expression pattern of adhesion molecules (ICAM-1 and VCAM-1), membrane attack complex (C5b-9), and major histocompatibility complex (MHC) antigens in muscle biopsy of mixed connective tissue disease (MCTD).


METHODS
We studied 14 patients with MCTD, and compared to 8 polimyositis (PM) patients, 5 dermatomyositis (DM) and 4 dystrophies. Inflammatory cells were examined for CD4+, CD8+, memory and naive T cells, natural killer cells, and macrophages. Expression of MHC-I and -II, ICAM-1, VCAM-1 and C5b -9 were characterized on muscle fibers and vessels.


RESULTS
Morphological analysis displayed a pattern of PM. Immunohistochemical study revealed a decreased number of capillaries, predominance of CD4+ and B cells in perivascular regions and predominance of CD8+ and CD45RO+ in endomysial regions. The expression of MHC-I on vessels and on degenerated muscle fibers, MHC-II expression on vessels and perifascicular muscle fibers, and the expression of ICAM-1 / VCAM-1 on endothelial cells indicated both vascular and cellular-immune mediated processes causing the muscular lesion.


CONCLUSIONS
Our findings revealed a mixed mechanism in MCTD, both vascular involvement as DM, and cell-mediated like PM.
Vianna
Maria Angela A G
MA
Division of Rheumatology, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brazil.
Borges
Claudia T L
CT
Borba
Eduardo F
EF
Caleiro
Maria Teresa C
MT
Bonfá
Eloisa
E
Marie
Suely K N
SK
D000328:Adult; D017677:Age Distribution; D015703:Antigens, CD / Q000276:immunology; D001323:Autoantibodies / Q000097:blood; D016516:CD4-CD8 Ratio; D015938:Complement Membrane Attack Complex / Q000276:immunology; D003882:Dermatomyositis / Q000276:immunology / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology*; D008285:Major Histocompatibility Complex / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D008947:Mixed Connective Tissue Disease / Q000276:immunology / Q000473:pathology; D011287:Prejudice; D011446:Prospective Studies; D019010:Vascular Cell Adhesion Molecule-1 / Q000276:immunology*
D015703:Antigens, CD; D001323:Autoantibodies; D015938:Complement Membrane Attack Complex; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1