Figure 1. Plasma from patients with IgAN contains poly-IgA complexes that are susceptible to reducing agent TCEP.

(A) Pooled plasma samples were collected from patients with IgAN (n = 8), and total IgA1 was extracted using jacalin-conjugated column. The extraction was then resolved by SEC, which was calibrated against molecular weight standards (arrowheads indicate kDa vs. elution volume along x axis). The IgA contents formed one major peak of mono-IgA, preceded by several overlapping minor peaks of poly-IgA and dimeric sIgA. (B) The poly-IgA fraction was subsequently analyzed by Western blotting with anti-human IgA heavy chain antibody under either reducing (R, with TCEP) or nonreducing (NR, without TCEP) conditions. With the addition of TCEP, the approximately 600 kDa poly-IgA complexes were reduced to an approximately 65 KDa band of IgA heavy chain (IgAH).