Impaired release of sCD23 by activated B-cells from RA patients

To determine the basis of a differential response among B-cells derived from rheumatoid arthritis (RA) patients and their normal counterpart to anti-CD3-activated T-cells (HUT-78 CD4+), B-cell responsiveness was measured in vitro with a focus on IgG and IgM secretion, the ability to differentiate into plasma cells, and the release of soluble CD23 (sCD23) into the culture media. In the patients with RA, plasma sCD23 levels were measured and studied to see if it related to the rheumatoid factor (RF) titer, age, sera immunoglobulin, therapy, and disease activity. Patients with RA were found to have a significantly increased level of sCD23 in the plasma when compared to control individuals, yet their peripheral blood B-cells were unable to secrete normal levels of sCD23 following in vitro stimulation by T-cells. The plasma level of sCD23 found in the RA patients correlated (P < 0.0001) with the RF titer. B-cells from the RA patients secreted significantly increased amounts of IgG and IgM after in vitro stimulation by T-cells. It appears that peripheral blood B-cells of RA patients are more activated initially and it is likely that at the time of coculture with T-cells they had already passed through the narrow window in cell maturation when sCD23 is released.