IgA nephropathy (IgAN) is the most common form of glomerulonephritis worldwide. The hallmark of the disease is depositions of polymeric IgA1 in the mesangium of the glomeuli. These depositions will... Show moreIgA nephropathy (IgAN) is the most common form of glomerulonephritis worldwide. The hallmark of the disease is depositions of polymeric IgA1 in the mesangium of the glomeuli. These depositions will lead to inflammation in the kidneys and eventually to deterioration of renal function. The pathogenesis of IgAN is not clear, but it is generally accepted that disturbances in the immune system of IgAN patients are responsible for this disease. In the current thesis we have investigated the immune response of IgAN patients in comparison with control persons. We have shown that IgAN patients have a hampered primary IgA immune response upon mucosal vaccination with a neoantigen, whereas a systemic vaccination with a neoantigen resulted in a similar immune response in both groups. We hypothesized that dendritic cells (DC), as professional antigen presenting cells could have an impaired function , or that less DC are present in the nasal mucosa. We were able to show that the number of DC present in the nasal mucosa of IgAN patients was not reduced as compared with controls. Using an in vitro model we studied the function of DC in the primary immune response and showed that DC of IgAN patients induced less IgA production in na_ve B cells than DC of control persons. Furthermore we studied the size distribution of the antigen specific IgA molecules in IgAN patients. In summary we showed that patients with IgAN have an impaired IgA production upon mucosal vaccination with a neoantigen and that at least part of this IgA hypo response is due to an impaired capacity of DC to induce IgA production, whereas the number of mucosal DC in IgAN patients is not reduced. Show less