R. Kittelberger et al., THE IMMUNOLOCALIZATION AND URINARY QUANTITATION OF 7-5Q A, A UNIQUE HUMAN RENAL ANTIGEN/, Clinical nephrology, 41(2), 1994, pp. 72-82
In this communication 7-5Q/A, a recently described human kidney-specif
ic acidic membrane glycoprotein, was immunolocalized by immunofluoresc
ence in kidney and placenta, and by immunogold electron microscopy in
the kidney. The antigen is located above and below the slit diaphragm
on epithelial cell foot processes in the glomerulus, and also on proxi
mal tubular brush border membranes. In the placenta it was present on
epithelial membranes. 7-5Q/A and dipeptidylpeptidase IV were compared
by a variety of techniques because of their similar size and possible
location, and found to be distinct. A sensitive sandwich ELISA was dev
eloped using polyclonal and monoclonal antibodies to 7-5Q/A, and appli
ed to the quantitation of this antigen in the urines and sera of patie
nts with a variety of kidney diseases, and in the urines and sera of n
ormal subjects. The concentration of 7-5Q/A in normal urines ranged fr
om 0 to 2 ng/ml but levels of up to 150 ng/ml were found in urines of
patients with renal disease. 7-5Q/A was not detectable in either norma
l or nephritic sera. Urinary quantitation of this unique antigen may b
e of value in the early diagnosis of renal disease.