Superdex 200 gel filtration and immunologic characterization of IL-6 in serum from patients with RA (n = 7) and patients with MDS (n = 6). (A) IL-6 concentrations of each fraction assayed using commercial MSD assay and (B) IL-6 concentrations of each fraction assayed using the panoptic IL-6 assay. IL-6, interleukin 6; MDS, myelodysplastic syndrome; MSD, Meso Scale Discovery; SEC, size exclusion column, RA 1, RA 2, RA 3, RA 4, RA 5, RA 6, RA 7, MDS 1, MDS 2, MDS 3, MDS 4, MDS 5, MDS 6