Chimeric cells of maternal origin do not appear to be pathogenic in the juvenile idiopathic inflammatory myopathies or muscular dystrophy.
BACKGROUND
Microchimeric cells have been studied for over a decade, with conflicting reports on their presence and role in autoimmune and other inflammatory diseases. To determine whether microchimeric cells were pathogenic or mediating tissue repair in inflammatory myopathies, we phenotyped and quantified microchimeric cells in juvenile idiopathic inflammatory myopathies (JIIM), muscular dystrophy (MD), and noninflammatory control muscle tissues.


METHODS
Fluorescence immunophenotyping for infiltrating cells with sequential fluorescence in situ hybridization was performed on muscle biopsies from ten patients with JIIM, nine with MD and ten controls.


RESULTS
Microchimeric cells were significantly increased in MD muscle (0.079 ± 0.024 microchimeric cells/mm(2) tissue) compared to controls (0.019 ± 0.007 cells/mm(2) tissue, p = 0.01), but not elevated in JIIM muscle (0.043 ± 0.015 cells/mm(2)). Significantly more CD4+ and CD8+ microchimeric cells were in the muscle of patients with MD compared with controls (mean 0.053 ± 0.020/mm(2) versus 0 ± 0/mm(2) p = 0.003 and 0.043 ± 0.023/mm(2) versus 0 ± 0/mm(2) p = 0.025, respectively). No differences in microchimeric cells between JIIM, MD, and noninflammatory controls were found for CD3+, Class II+, CD25+, CD45RA+, and CD123+ phenotypes, and no microchimeric cells were detected in CD20, CD83, or CD45RO populations. The locations of microchimeric cells were similar in all three conditions, with MD muscle having more microchimeric cells in perimysial regions than controls, and JIIM having fewer microchimeric muscle nuclei than MD. Microchimeric inflammatory cells were found, in most cases, at significantly lower proportions than autologous cells of the same phenotype.


CONCLUSIONS
Microchimeric cells are not specific to autoimmune disease, and may not be important in muscle inflammation or tissue repair in JIIM.
Department of Microbiology and Immunology, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA, 19129, USA. carol.artlett@drexelmed.edu.
Carol M
CM
Artlett
Department of Microbiology and Immunology, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA, 19129, USA. Sihem.sassi-gaha@drexelmed.edu.
Sihem
S
Sassi-Gaha
Department of Medicine, Thomas Jefferson University, 1020 Walnut Street, Philadelphia, PA, 19107, USA. Rramos@agisglobal.com.|Present address: Agis Global, Business Development Executive, 1266 East Main Street, Stamford, CT, 06902, USA. Rramos@agisglobal.com.
Ronald C
RC
Ramos
National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Environmental Autoimmunity Group, Program of Clinical Research, 9000 Rockville Pike, Bethesda, MD, 20892, USA. millerf@mail.nih.gov.
Frederick W
FW
Miller
National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Environmental Autoimmunity Group, Program of Clinical Research, 9000 Rockville Pike, Bethesda, MD, 20892, USA. riderl@mail.nih.gov.
Lisa G
LG
Rider
D000293:Adolescent; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D019070:Cell Lineage / Q000235:genetics / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D002678:Chimera / Q000276:immunology* / Q000378:metabolism; D046528:Chimerism; D005260:Female; D006801:Humans; D006822:Hybrid Cells / Q000276:immunology / Q000378:metabolism; D016130:Immunophenotyping; D017404:In Situ Hybridization, Fluorescence; D018655:Lymphocyte Count; D008431:Maternal-Fetal Exchange / Q000235:genetics / Q000276:immunology; D008856:Microscopy, Fluorescence; D009136:Muscular Dystrophies / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D009220:Myositis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011247:Pregnancy