title: Differential sensitivity to transforming growth factor (TGF)-beta of CBA and of CBA/N B cells demonstrates that the IgG2b inducing factor in synovial fluid from rheumatoid arthritis patients is not identical to TGF-beta.
abstract: Synovial fluid from patients with rheumatoid arthritis (RA-SF) contains in vivo produced cytokines and inflammatory mediators, including a factor that induces IgG2b production of lipopolysaccharide (LPS) preactivated murine B lymphocytes. In order to determine the mechanism by which RA-SF acts on LPS activated mouse B cells, CBA/N mice were used as an experimental model. The X-linked immunodeficiency of these mice is caused by a point mutation in the Bruton's tyrosine kinase (btk) gene. We have earlier shown that RA-SF can reconstitute the CBA/N B cell deficiency in vitro and in vivo, with regard to IgG2b production after LPS stimulation. Since transforming growth factor (TGF)-beta has been suggested to be a switch factor for IgG2b, we aimed at investigating the role of TGF-beta in our experimental system. We found that TGF-beta could not mimic the effect of RA-SF on CBA spleen cells. A small increase of IgG2b secretion was observed with spleen cells from normal CBA mice, whereas Ig secretion of all isotypes was suppressed in CBA/N spleen cells treated with TGF-beta at any concentration. Neutralizing antibodies against TGF-beta suppressed the response of CBA B cells, whereas the response by CBA/N B cells was enhanced by the same antibody preparation. Here we also show that the abnormal B cell responsiveness to TGF-beta, typical of CBA/N, co-segregates with the btk mutation in male (CBA x CBA/N)F2 spleen cells. This was determined by allele specific PCR recognizing the identified base substitutions of the btk gene, typical of the two strains. We propose that RA-SF contains a factor, separate from TGF-beta, that is involved in the differentiation of IgG2b expressing cells.
authors.affiliation: Department of Immunology, Arrhénius Laboratories for Natural Sciences, Stockholm University, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Ridderstad
authors.forename: H
authors.initials: H
authors.lastname: Lettesjö
authors.forename: M
authors.initials: M
authors.lastname: Abedi-Valugerdi
authors.forename: E
authors.initials: E
authors.lastname: Möller
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000483:Alleles; D000818:Animals; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D001483:Base Sequence; D001685:Biological Factors / Q000302:isolation & purification* / Q000494:pharmacology; D004252:DNA Mutational Analysis; D005260:Female; D007074:Immunoglobulin G / Q000096:biosynthesis* / Q000235:genetics; D007153:Immunologic Deficiency Syndromes / Q000235:genetics / Q000276:immunology*; D015847:Interleukin-4 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects*; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000235:genetics; D013582:Synovial Fluid / Q000737:chemistry*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014960:X Chromosome
chemical_list: D001685:Biological Factors; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D016212:Transforming Growth Factor beta; D015847:Interleukin-4; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse