HLA-A and hemochromatosis: Aims of this study are 1) to characterize serum IgG subclass levels at diagnosis in a replication cohort of 157 referred hemochromatosis probands with HFE p.C282Y homozygosity and HLA-A and -B typing/haplotyping, 2) to investigate laboratory and clinical associations with IgG subclass levels of this cohort, and 3) to compare mean and relative levels of IgG subclasses levels of this cohort with those of eight previously published adult cohorts unselected for hemochromatosis diagnoses.