Binding parameters (B_max and K_d) of ¹²⁵I-labeled FKN to PBMCs from VI individuals are reduced compared with PBMCs from VV individuals.

¹²⁵I-labeled FKN bound specifically to freshly isolated PBMCs. With the use of a nonlinear regression equation based on a single class of FKN binding sites, the total number of FKN binding sites (B_max) and the apparent FKN affinity (K_d) were extrapolated from the saturation binding curves. B_max, expressed as the number of FKN binding sites per cell (A), and K_d, expressed as pM (B), were plotted as a function of the CX3CR1 V249I genotypes: VV-TT (▪), VI-TT (●), VI-TM (○), II-TT (▴), II-TM (⋄), and II-MM (▾). Significance by analysis of variance was P < .05 for the B_max and the K_d values. P values on the figure indicate the significance of the comparison between VV and VI genotypes (protected least significant difference Fisher test). Note that the B_max and K_d values reported here for the reference genotype (more than10 000 sites per cell with an apparent affinity of 100 pM) are different from those in our previous report (2800 sites per cell with 12 pM affinity).5 The difference may be explained by differences in the study populations: thawed PBMCs from HIV patients in the initial report versus freshly isolated PBMCs from healthy subjects in the present study, and binding conditions of room temperature versus 37°C.