¹²⁵I-Eotaxin binds human thymocytes with high affinity. (A) Homologous competition using unlabeled eotaxin shows displacement of labeled eotaxin from rigorously purified thymocytes. Scatchard analysis shows a kd of 2 nmol/L and approximately 1,100 eotaxin-binding sites per cell across the entire population. The displacement and Scatchard curves are representative of n = 4 experiments. (B) Heterologous competition of ¹²⁵I-Eotaxin using unlabeled MCP-2, MCP-3, MCP-4, IL-8, and Gro-. The histograms are the mean ± SE mean displacements from a single experiment in which each point was performed 6 times. The experiment is representative of n = 3 other analyses. (C) RT-PCR analysis of CCR-3 expression on the entire thymocyte population. PCR was performed using cloned full-length CCR-3 cDNA as a control. (D) The PCR product was transferred and probed using an internal ³²P-labeled oligomer to human CCR-3, as described in Materials and Methods.