T and B cell responses following immunization with tetanus toxoid in IgA nephropathy
The B and T cell responses were investigated in IgA nephropathy before and after immunization with tetanus toxoid (TT). Both IgA and IgG anti‐tetanus toxoid antibodies were elicited, but the IgA ntibodies were significantly greater in patients (92·6 ± 11·7 ELISA units) than in the controls (49·2 ± 7·5 ELISA units). This was associated with a significantly greater proportion of IgA+ B cells in patients than controls before immunization. However, a significant increase in the proportion of IgA 1 binding CD4 and CD8 cells was also found. The proportion of CD3 cells with γδ T cell receptors (CD3+TCRγδ+), was significantly greater before immunization in the IgA nephropathy patients 37·0%± 2·4), compared with controls (100%± 2·3; P < 0·001). Immunization with TT further enhanced the CD3+TCRγδ5+ cells in patients to 45·8%± 7·2 compared with controls (16·3%± 4·5), with a corresponding decrease in CD3+TCRαβ+ cells in the patients (P < 0·001). CD3+TCRγδ+ cells are upregulated by common microbial antigens and clinical exacerbations of IgA nephropathy are frequently associated with mucosal infections and a rise in serum IgA concentration. The increased TCRγδ (5 expression may be responsible for the enhanced IgA antibody response in IgA nephropathy. The increase in IgA antibodies may then exert a controlling effect by binding to augmenting T cells and thereby inhibiting their function.