Renal subcapsular tertiary lymphoid aggregates in chronic kidney diseases

In the last decade, it has been accepted the formation of tertiary lymphoid organs in the renal parenchyma during inflammatory conditions. These organized cellular aggregates contain B- and T-lymphocytes, dendritic cells, surrounded by neo-lymphatic vessels. They have been described in renal allografts, acute and chronic interstitial nephritis, IgA and membranous nephropathies. The functional characteristics of these lymphoid nodules remained still under consideration. After investigating the renal biopsies of 268 patients with primary and secondary nephropathies, we have selected 20 cases showing lymphoid-like cellular aggregates located just beneath the renal capsule and having close contacts with this kidney envelope. All of these cases also showed an associated medium sized lymphatic vessel. The ultrastructure of these nodules proved to contain more or less the same cellular composition: lymphocytes, dendritic cells, seldom plasma cells and macrophages. We consider these particular subcapsular lymphoid-like nodules to be tertiary lymphatic structures in close association with the perirenal lymphatics, and the first to develop in any type of inflammatory and autoimmune renal condition.