Trafficking of inflammatory macrophages from the kidney to draining lymph nodes during experimental glomerulonephritis

Macrophage accumulation within the glomerulus and renal interstitium is a prominent feature of most forms of glomerulonephritis, but the fate of these inflammatory cells is unknown. Macrophage trafficking to the draining kidney lymph nodes (KLN) was assessed in a detailed kinetic analysis of accelerated antiglomerular basement membrane (GBM) disease in the rat. Leucocytes draining to KLN via lymphatic vessels were identified within the marginal sinus by MoAb labelling of tissue sections. In anti-GBM disease, there was a significant increase in the weight of the KLN due to both lymphoproliferation within the nodes and increased lymphatic drainage from the inflamed kidney, as evidenced by prominent dilation of the marginal sinus and increased numbers of cells within the sinus. In non-inflamed lymph nodes, few ED1⁺ macrophages were present within the marginal sinus (3.0 ± 0.6/100 nucleated cells). However, in anti-GBM disease, macrophages became the major cell type within the dilated marginal sinus of the KLN, as shown by labelling with ED1, ED2 and ED3 MoAbs, peaking at 74 ± 2.6 ED1⁺ cells/100 nucleated cells at day 14. These changes were not simply due to systemic antigen administration, since in the axillary lymph node (ALN) there was no obvious dilation of the marginal sinus and macrophages accounted for a maximum of only 15 ± 4.6 ED1⁺ cells/100 nucleated cells. In conclusion, this study provides indirect evidence that there is significant trafficking of the renal macrophage infiltrate to the KLN during experimental glomerulonephritis. This may be a mechanism whereby nephritogenic antigens, released as a consequence of the local inflammatory response, may be presented to T and B lymphocytes within lymph nodes, resulting in the amplification of the immune response in glomerulonephritis.