Pediatric Rheumatology Online Journal →
June 2003 → Epidemiology, Classification, Immunology and Immunogenetics →
Abstract #10
DISEASE-SPECIFIC IgM RHEUMATOID FACTOR EXPRESSION BY TONSIL-DERIVED B CELLS DEPENDS UPON THE INHIBITION OF APOPTOSIS
D. Milojevic,1 V. R. Bonagura.2
1Pediatric Rheumatology, Schneider Children's Hospital, NS LIJ Health System, New Hyde Park, NY; 2Division of Allergy and Immunology, Schneider Children's Hospital, NS LIJ Health System, New Hyde Park, NY
Disease-specific (D-S) IgM rheumatoid factors (RFs) that bind IgG3 are commonly expressed by rheumatoid arthritis (RA) patients, but rarely by individuals without RA. To determine if defective peripheral regulation of D-S RF expression may be present in RA, we inhibited thymus derived (T-D) B-cell apoptosis in an individual without RA and then screened for D-S RF expression by ELISA.
METHODS: T-D B-cells were fused with NSO mouse myeloma cells, containing the anti-apoptotic bcl-2 gene (NSObcl-2), or NSO wild-type cells (NSOwt) without bcl-2, or were transformed with Epstein Barr Virus (EBV) containing "bcl-2 like" genes. Clones were isolated by picking from agar, D-S RF specificity determined by ELISA, and clonality identified by VH immunoglobulin gene sequencing.
RESULTS: 0.83% of NSObcl-2-B-cell hybrids produced RFs. 85% of RFs bound IgG3. 35% exclusively bound IgG3, 20% bound IgG1 and 3 only, 20% were pan-binding (IgG1-4), 5% bound IgG3 and 4 only, and 5% bound IgG2, 3 and 4 only. 0.76% of the EBV transformed B-cells produced RFs. D-S, IgG3 binding was present in 64%. Of these, 7.3% bound IgG3 only, 20.5% bound IgG1 and 3 only, 14.7% are pan-binders (IgG1-4), 19.1% bound IgG1, 3 and 4 only, 1.4% bound IgG1,2 and 3 only, and 1.4% bound IgG3 and 4 only. None of the NSOwt- T-D B-cell hybrids expressed RFs.
CONCLUSIONS: Inhibition of T-D B-cell apoptosis permits D-S RF expression. The RF repertoires produced by T-D B-cell-NSObcl-2 hybrids and EBV transformed lymphoblasts differ dramatically from that expressed by T-D B-cell NSOwt hybrids. Thus, defective peripheral regulation of D-S IgM RF production by RA patients may permit D-S RF expression, and implicate RF immune dysregulation in RA pathogenesis.