Expression of CD19(+)CD5(+)B cells and IgA1-positive cells in tonsillar tissues of IgA nephropathy patients.

The hallmark of IgA nephropathy (IgAN) is the mesangial deposits of polymeric IgA. However, the source of IgA1 and the mechanism of deposition of IgA1 in the mesangium remain unknown. To better understand its pathogenesis, we investigated the expression of CD19(+)CD5(+)B cells and IgA1-positive cells in the tonsils of IgAN patients. Immunofluorescence was used to visualize the locations of CD19(+)CD5(+)B cells and IgA1-positive cells in the tonsils. In this study, it was demonstrated that CD19(+)CD5(+)B cells are usually found in germinal centers and in the capsule covering the upper parts of the nodules of lymphoid tissue (cap of the nodule). The expression of IgA1-positive cells in tonsil tissue can be seen in the cap of the nodule and subepithelial tissue. There is a significant relationship between IgA1 and CD19(+)CD5(+)B cells. The level of CD19(+)CD5(+)B cells is positively correlated to the severity of renal pathological changes. These findings suggest that CD19(+)CD5(+)B cells in the tonsils could have an impact on the pathogenesis of IgAN.