Fig. 4.
Antigen-specific immunoglobulin A (IgA) after systemic immunization consists almost exclusively of polymeric IgA (pIgA). IgA of serum was size-fractionated with a HiLoadTM 16/60 HR200 Superdex prep grade gelfiltration column. Total IgA and keyhole limpet haemocyanin (KLH)-specific IgA were determined by enzyme-linked immunosorbent assay (ELISA). (a) Serum profile of an IgA nephropathy (IgAN) patient for KLH-specific IgA (black line) and for total IgA (dotted line). Concentrations of high molecular weight IgA (pIgA) and of low molecular weight IgA [monomeric IgA (mIgA)] in serum were determined by ELISA for total and KLH-specific IgA. (b) Percentages of KLH-specific mIgA and pIgA of six controls and six IgAN patients.