ABSTRACT
AIM: To investigate whether transferrin rec ep tor (TfR) and Fc ?/? R are the major IgA 1 receptor on human mesangial cells (HMC). METHODS: Serum IgA 1 was isolated by jacalin affinity chromatog raphy and heated to aggregated form (aIgA 1). RT-PCR was performed to investiga te the expression of TfR mRNA and Fc?/?R mRNA. Binding capacity of aIgA 1 to human mesangial cell line (HMCL) was evaluated by radio-ligand binding assay. Bi nding specificity was determined by competitive inhibition assay and phosphoryla tion of extracellular signal-regulated kinase (ERK) was determined by Western bl ot. RESULTS: TfR cDNA and Fc?/?R cDNA products were amplified from HMC but not from HMCL. aIgA 1 was found to bind to HMCL in a dose-dependent, s aturable manner and the binding was inhibited by BSA. Scatchard analysis reveale d a Kd of (6.4?1.7)?10 -7 mol/L and the binding sites were (3.0?1.2) ?106/cells. Both aIgA 1 from patients with IgAN and healthy controls were ab le to induce the phosphorylation of ERK in a similar time-dependent manner, but the effect of aIgA 1 from patients with IgAN was much stronger (P