Clinical involvement of the tonsillar immune system in IgA nephropathy.

The temporal association of tonsillitis and hematuria or proteinuria in IgA nephropathy suggests that there might be a link between the physiological properties of the secondary lymphoid organ that tonsils represent and the mesangial deposition of IgA characteristic of this nephropathy. A number of clinical and ex-vivo data support this hypothesis. One of the earliest was the demonstration of the dimeric nature of mesangial IgA, composed of IgA monomers linked by a J chain, yet lacking the polyIg receptor acquired by secretory IgA during transcytosis through epithelial cells. This molecular structure is that of IgA synthesized in human tonsils, the epithelium of which lacks polyIg receptor. Moreover, tonsils from patients with IgA nephropathy display an abnormal partition of IgG and IgA producing plasma cells associated with a significantly developed web of high endothelial venules. IgA nephropathy could thus be in part related to an alteration of IgA precursors homing in tonsils. Tonsillectomy thus would present the advantage of removing an abnormally functioning source of dimeric IgA. Performed early enough in the course of the renal disease, tonsillectomy could suffice to halt the development of the nephropathy and restore the kidneys to health.