Cationic charge-preferential IgG reabsorption in the renal proximal tubules.
BACKGROUND
The brush border of the renal proximal tubules has a polyanionic charge. Since immunoglobulin G (IgG) molecules have a wide range of charge diversity, reabsorption of urinary IgG molecules are supposed to be influenced by the electrostatic interaction.


METHODS
Charge diversity of serum and urinary IgG molecules in patients with various renal diseases (N= 12) and premature neonates (N= 3) were analyzed by isoelectric focusing and Immunoblotting.


RESULTS
In patients with glomerular diseases, urinary IgG was solely composed of neutral and anionic IgG, whereas that of the cationic part (isoelectric point >8) was not observed. By contrast, in patients with proximal tubular diseases (Dent's disease and idiopathic Fanconi syndrome), the proportion of the cationic IgG was similar to that of serum IgG. In addition, the cationic part of IgG in the urine was found in the neonates with a gestational age of 28 and 31 weeks, but not found in those of 35 weeks.


CONCLUSIONS
The results suggest that renal proximal tubules reabsorb the urinary IgG in a cationic preferential way, and this mechanism requires renal maturation.
Department of Pediatrics, Nihon University School of Medicine, Tokyo, Japan. shori@med.nihon-u.ac.jp
Shori
S
Takahashi
Naohiro
N
Wada
Kensuke
K
Harada
Michio
M
Nagata
D000293:Adolescent; D000328:Adult; D002412:Cations / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005198:Fanconi Syndrome / Q000276:immunology* / Q000378:metabolism; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000737:chemistry / Q000378:metabolism; D007074:Immunoglobulin G / Q000737:chemistry / Q000378:metabolism*; D007231:Infant, Newborn; D007234:Infant, Premature; D007526:Isoelectric Point; D007687:Kidney Tubules, Proximal / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism*; D008297:Male; D009404:Nephrotic Syndrome / Q000276:immunology* / Q000378:metabolism
D002412:Cations; D007070:Immunoglobulin A; D007074:Immunoglobulin G