Objective: To determine whether anti-TNF alpha (infliximab) treatment affects B cell activation in patients with rheumatoid arthritis (RA) METHODS: B cell activation was analyzed in fifteen anti-TNF-treated RA patients. CD23 expression was used as a B cell activation marker and was studied before and after three months of infliximab treatment. PBMC were stimulated with anti-CD3 mAb during 18 h and were separated by rosseting into E+ and E-cells. B cells were assessed in E-population by double staining with CD19 and CD23. ELISA assays were used to assess both soluble TNF alpha and circulant immune complexes (CIC) containing TNF alpha. We also used B cells from tonsils to establish the relationship between B cell activation and TNF alpha CIC.
Results: The proportion of B cells expressing CD23 was higher before infliximab exposure than after treatment (48.3 +/- 16.7 versus 29.5 +/- 12.5, p = 0.007). T-B cell interactions were assessed by means of blocking antibodies to CD154, CD40, CD69, and CD18; these interactions were not specially affected by infliximab treatment. We could demonstrate CIC containing TNF alpha after infliximab treatment, these CIC, similarly to others IgG-containing immune complexes, were capable to downregulate CD23 on B cells.
Conclusions: Infliximab treatment in RA downregulates CD23 expression on T-cell activated B cells. This downregulation is connected with the presence of CIC containing TNF alpha. Presumably, the Fc gamma RIIb1 endows IgG-containing immune complexes, as TNF alpha-anti-TNF alpha, with the capacity to regulate B cells and inflammatory cells.