Urine IgG2/IgG4-ratio indicates the significance of the charge selective properties of the glomerular capillary wall for the macromolecular transportin glomerular diseases

Background. Alterations of the charge-selective properties of the glomerula r capillary wall are important constituents of the pathogenesis of many glo merular diseases. Thus, differences in the degree of such changes could be of help in understanding the mechanisms governing the transport of macromol ecules across the glomerular capillary wall. Methods, The ratio between urine concentrations of neutral IgG2 and negativ ely charged IgG4 (IgG2/IgG4-ratio) was measured in 150 proteinuric patients and 21 healthy controls. The patients were subdivided into seven biopsy ve rified diagnostic groups. Results. The study revealed decreased IgG2/IgG4-ratio in membranous glomeru lonephritis (0.57)compared to healthy controls (2.09) and to all other diag nosis groups; crescentic necrotizing glomerulonephritis (1.28), diffuse pro liferative glomerulonephritis (1.10), IgA nephropathy (1.11), mesangial pro liferative glomerulonephritis (1.55), minimal change nephropathy (1.00), an d nephrosclerosis secondary to hypertension (1.06). Although not statistica lly significant, there was a tendency towards lower IgG2/IgG4-ratio values in all the studied glomerular diseases compared to healthy controls. Conclusions. Since IgG is transported entirely through the large pores of t he glomerular basement membrane decreased IgG2/IgG4-ratio implies that this pathway is strongly influenced by the charge-selective properties of the g lomerular capillary wall. The conclusion that could be drawn from that is t hat the large pore radius must be discrete, in the order of 80-90 Angstrom, and thus not non-discriminatory to macromolecules as previously thought.