Fig. 3: Ligand selectivity of CD163.

a The structure of the CD163 trimer bound to HpHb viewed from three directions, showing that each arm of CD163 interacts differently with the HpHb ligand. b Schematic showing the different stoichiometries and structures of the ligands studied here. c A view of SRCR2 of CD163_A (violet) bound to Hp (green). Below is shown a partial sequence alignment of Hp and Hpr. Residues which differ between Hp and Hpr and which might influence binding to CD163 are shown as sticks and are labelled. d Assessment of the binding of CD163 ectodomain, immobilised through a C-terminal biotin, to Hp(1-1)Hb, Hp(2-2)Hb, HpSPHb and HprSPHb by SPR analysis. These represent twofold dilution series from a maximum concentration of 10 nM for Hp(1-1)Hb and Hp(2-2)Hb, 20 nM for HpSPHb, as well as an injection at 20 nM of HprSPHb. Data were shown as black lines, while fitting to a one-to-one binding model is depicted as dashed red lines. These are representative of n = 3. e Assessment of the binding of Hp and Hb to the CD163 ectodomain using MST. Each point is the mean of three replicates, and the error bars are the standard deviation. f Measurement of the ability of different ligands to compete for the uptake of fluorescently labelled Hp(2-2)Hb into HEK293 cells transfected with CD163. BSA is included as a control for CD163-independent effects. Each point represents the mean of three replicates, and the error bars are standard deviations.