Protein A immunoadsorption cannot significantly remove the soluble receptor of urokinase from sera of patients with recurrent focal segmental glomerulosclerosis.
BACKGROUND
Focal segmental glomerulosclerosis (FSGS) is a serious disease, the pathogenesis of which is unknown. Its recurrence after transplantation (Tx) and its partial remission after treatment with immunoadsorption (IA) on a protein A column indicate the existence of a circulating factor responsible for the disease that is able to bind to a protein A column. Recently, the soluble receptor of urokinase (suPAR) was described as the factor responsible for FSGS. We tested the capacity of suPAR to bind to protein A and to be eliminated by IA.


METHODS
We measured suPAR in eluates of protein A columns from seven patients with recurrent FSGS after Tx (rFSGS) treated with IA, and in the serum of 13 patients with rFSGS and 11 healthy donors (HDs). Additionally, the plasma of these patients was immunoadsorbed in vitro on a protein A Sepharose column, and we quantified suPAR in the eluates and in pre- and post-column samples.


RESULTS
The concentration of suPAR was higher in the plasma of patients with rFSGS than that of HD patients. However, the concentration of suPAR was similar before and after IA on protein A for the rFSGS and HD samples. The suPAR concentration was very low in the eluates from protein A columns incubated with plasma from HD or rFSGS patients. However, 85% of rFSGS patients showed a decrease in immunoglobulin G and proteinuria.


CONCLUSIONS
Thus, suPAR does not significantly bind to protein A in vitro or in vivo.
Nephrology Department, IFRNT, Le Kremlin Bicêtre, France.
Severine
S
Beaudreuil
Xiaomeng
X
Zhang
Faycal
F
Kriaa
Jacques
J
Dantal
Helene
H
Francois
Aimé
A
Vazquez
Bernard
B
Charpentier
Hans-Kristian
HK
Lorenzo
Antoine
A
Durrbach
D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005923:Glomerulosclerosis, Focal Segmental / Q000097:blood / Q000276:immunology / Q000628:therapy*; D006084:Graft Rejection / Q000276:immunology / Q000517:prevention & control; D006801:Humans; D007163:Immunosorbent Techniques; D016030:Kidney Transplantation; D008297:Male; D055293:Receptors, Urokinase Plasminogen Activator / Q000097:blood*; D012008:Recurrence; D012189:Retrospective Studies; D013205:Staphylococcal Protein A
D055293:Receptors, Urokinase Plasminogen Activator; D013205:Staphylococcal Protein A
focal and segmental glomerulosclerosis; immunoadsorption; protein A Sepharose column; soluble urokinase plasminogen activator receptor