VH3-21 B-CELLS ESCAPE FROM A STATE OF TOLERANCE IN RHEUMATOID-ARTHRITIS AND SECRETE RHEUMATOID-FACTOR

Background: Rheumatoid factor (RF) is a characteristic but not pathogn omic feature in patients with rheumatoid arthritis (RA). It is unknown whether the repertoire of immunoglobulin genes utilized by RF(+) B ce lls of RA patients is unique and whether RF(+) B cells in normal indiv iduals are silenced or deleted. Materials and Methods: Clonal B cell p opulations were established from the peripheral blood of normal donors (127 B cell clones), RA patients (113 RF(-) and 60 RF(+) B cell clone s) and patients with primary Sjogren's syndrome (82 RF(-) and 47 RF(+) B cell clones) by coculturing with anti-CD3-stimulated T helper cell clones. The cross-reactivity pattern of antibodies secreted by the B c ell clones was determined by ELISA on a panel of antigens. The molecul ar structure of the IgM heavy chains was characterized by VH family-sp ecific RT-PCR and sequencing. VH elements which correlated with RF spe cificity were identified. The responsiveness of B cells expressing the se VH elements to T helper cell signals was compared in normal individ uals and RA patients. Results: The majority of RF(+) B cells were mono specific when specificity was tested on five antigens. RF(+) B cells e xpressed a significantly different repertoire of VH gene segments than RF(-) B cells. In particular, the VH3 gene segment V3-21 was not dete cted in B cell clones from normals but was the most frequent VPI eleme nt in RF(+) B cell clones from RA patients. Most of the V3-21 sequence s were in germline configuration. The correlation between RF specifici ty and V3-21 gene segment usage was maintained in patients with Sjogre n's syndrome. V3-21 transcripts were present in peripheral blood R cel ls from normal individuals. VH3-21(+) B cells from RA patients but not from normal donors wore responsive to preactivated T helper cells. St imulation with a bacterial superantigen could overcome the nonresponsi veness of V3-21(+) B cells in normal donors anti induce the secretion of RF. Conclusions: RF production is correlated with the usage of the V3-21 gene segment in two distinct RF(+) diseases. in patients with th ese diseases, V3-21(+) B cells secrete antibodies with RF activity in response to activated T helper cells. V3-21(+) B cells remain in a sta te of nonresponsiveness in normal individuals that can be broken by su perantigen stimulation. The germline configuration of VH3-21(+) RF(+) immunoglobulins in RA patients suggests that the loss of tolerance is not an antigen-driven process.