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IgG2b Inducing Factor from Rheumatoid Arthritis Synovial Fluid Activates Antibody Production in Highly Purified Mouse B Lymphocytes
Author(s) -
LETTESJO¨ H.,
MO¨LLER E.
Publication year - 1997
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1046/j.1365-3083.1997.d01-373.x
Subject(s) - bruton's tyrosine kinase , antibody , b cell , microbiology and biotechnology , in vitro , synovial fluid , rheumatoid factor , immunology , biology , tyrosine kinase , receptor , chemistry , medicine , biochemistry , alternative medicine , pathology , osteoarthritis
Rheumatoid arthritis synovial fluid (RA‐SF) contains a factor that induces IgG2b antibody production in LPS‐stimulated murine B cells and therefore is called IgG2b inducing factor (IgG2bIF). When LPS, together with crude RA‐SF or semi‐purified IgG2bIF, was added to highly purified LPS‐stimulated B cells, the number of IgG2b‐producing cells was substantially enhanced. This shows that IgG2bIF acts directly on activated B cells, presumably by binding to a receptor expressed on LPS‐activated B cells. In vivo LPS‐activated B blasts were not able to respond to RA‐SF unless LPS was present in vitro , showing that LPS is needed to maintain cell viability and responsiveness to the IgG2bIF. To elucidate the mechanism for the IgG2bIF effect on highly purified B cells, the IgG2b response of LPS‐stimulated, Bruton's tyrosine kinase‐defective, xid B blasts was studied. Purified B blasts from the btk ‐defective CBA/N mouse strain were sensitive to IgG2bIF. These findings show that IgG2bIF acts directly on B cells and activates cells through a btk ‐independent pathway.