Genomic imprinting of insulin-like growth factor 2 (IGF-2) in chronic synovitis.
OBJECTIVE
To search for relaxation or loss of IGF-2 imprinting (LOI) in rheumatoid arthritis (RA) synovial tissues.


METHODS
The genotype of IGF-2 was determined in 25 freshly isolated synovial tissue samples with signs of active inflammation by polymerase chain reaction (PCR) and restriction fragment length polymorphism. Imprinting was determined in synovial tissue mononuclear cells (STMC) of five informative heterozygous patients by reverse transcriptase (RT)-PCR. Mitogen-stimulated peripheral blood mononuclear cells (PBMC) from six informative healthy donors were selected for control.


RESULTS
In vitro proliferation of CD4+ and CD8+ PB T cells, and also of CD19+ PB B cells was detectable upon mitogen stimulation. Furthermore, MHC II molecule expression on synovial B and T cells indicated in vivo cell activation. Monoallelic IGF-2 expression was seen in PBMC cultures from two healthy donors under both, resting and stimulating conditions. In two other PBMC cultures, LOI occurred exclusively after 24 h of stimulation. PBMC from two other healthy donors showed LOI under both, resting and stimulating conditions. Mitogen induced and spontaneous LOI was reversible in each one PBMC culture after 72 h. In contrast, none of the informative STMC cultures showed LOI.


CONCLUSIONS
LOI in lymphocytes may occur spontaneously or inducible. However, longstanding activation of lymphocytes in RA synovitis appears not to be related to this mechanism.
Möller
B
B
Inselspital - University Hospital Bern, Klinik für Rheumatologie, klinische Immunologie und Allergologie, CH-3010 Bern, Switzerland. burkhard.moeller@insel.ch
Kerschbaumer
G
G
Komor
M
M
Kerschbaumer
F
F
Ottmann
O G
OG
Hoelzer
D
D
Hofmann
W K
WK
D000293:Adolescent; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000235:genetics* / Q000276:immunology; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D002908:Chronic Disease; D005260:Female; D018392:Genomic Imprinting; D006579:Heterozygote; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000235:genetics; D008297:Male; D008875:Middle Aged; D008934:Mitogens / Q000494:pharmacology; D013583:Synovial Membrane / Q000276:immunology*; D013585:Synovitis / Q000235:genetics* / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology
C035170:IGF2 protein, human; D008934:Mitogens; D007335:Insulin-Like Growth Factor II