CD79A and sclerosing cholangitis: Frequency of IgA and IgG against GP2 isoforms 1 (aGP21) to 4 (aGP24) detected by indirect immunofluorescence assay on stabile isoform-transduced HEp2 cells in 212 patients with primary sclerosing cholangitis (PSC) from different hospitals and 145 controls.