Inflammation, Vol. 24, No. 6, 2000 0360-3997 / 00 / 1200-0519$18.00 / 0  2000 Plenum Publishing Corporation 519 RECEPTOR MEDIATED ENDOCYTOSIS BY MESANGIAL CELLS MODULATES TRANSMIGRATION OF MACROPHAGES P. C. SINGHAL, S. GUPTA, P. SHARMA, H. SHAH, N. SHAH, and PUJA PATEL Departments of Medicine and Pathology Long Island Jewish Medical Center New Hyde Park, New York 11040 The Long Island Campus for Albert Einstein College of Medicine Bronx, New York 10461 Abstract—Background: Accumulation of immune complexes in the mesangium is a common finding. Since migration of macrophages (Mf) in the mesangium has been demonstrated to be an important event in the development of glomerular lesions, we studied the role of immune complexes and mesangial cell (MC) interaction in the transmigration (Tm) of Mf. Methods: To determine the effect of MC and immune complexes (aggregated IgG, IgGAg) on transmigration of Mf, MC were incubated with or without IgGAg in the lower compartment of a modified Boyden Chamber. To determine the effects of the secretory products (as a result of endocytosis of IgGAg by mesangial cells), MC-IgAg conditioned media was prepared and placed in the lower compartment of the Boyden chamber. We evaluated the effects of MC alone, MC + IgGAg, or MC-IgGAg conditioned media on the transmigration of macrophages across a filter. To determine the effect of free radicals on MC-IgAg endocytosis-induced Mf migration we evaluated the effect of free radical scavengers such as dimethyl thiourea (DMTU) and tetramethylthiourea (TMTU) in MC-IgAg endocytosis-induced Mf migration. To determine the role of chemokines in MC-IgAs endocytosis-induced Mf migration we evaluated the effect of ani-MCP-1 antibodies on MC-IgAg endocytosis-induced Mf migration, and also studied the effects of IgAg on MC mRNA expression of MCP-1 and RANTES. In addition, we evaluated the role of Fc receptors and actin cytoskeleton of MC in transmigration of Mf. Results: Mesangial cell endocytosis of IgG aggregates (IgGAg) is associated with enhanced (P < 0.001) transmigration of Mf (control, 11.2 ± 0.2 vs. MC + IgGAg, 22.1 ± 0.9 migrated Mf / field). IgGAg also induced MC mRNA expression for RANTES and MCP-1 on MC. DMTU and TMTU attenuated (P < 0.001) the MC + IgGAg-induced migration of Mf as well as IgGAg-induced mRNA expression for RANTES and MCP-1. MC and IgGAg interaction products (MC-IgGAg conditioned media) also increased (P < 0.01) transmigration of Mf (control, 18.3 ± 1.7 vs. MC-IgGAg conditioned media, 30.7 ± 0.6 Mf / field). This effect of MC-IgGAg conditioned media on the migration of macrophages was dose dependent. Anti-MCP-1 antibody partially inhibited MC-IgGAg-induced migration of macropahges. MC and monomeric IgG (MIgG) interaction (MC-MIgG conditioned