CCR8 is expressed by post-positive selection thymocytes, and CCR8 ligands are expressed by medullary thymic stromal cell subsets.

<p>(A) qRT-PCR analysis was used to quantify relative <i>Ccr8</i> expression levels in FACS-sorted thymocyte subsets. Expression was normalized first to β-actin levels in each sample, and then between samples to expression in the CD4⁺ CD69⁺ subset. Graph shows means + SD of technical triplicates from one representative of three independent experiments. (B) Flow cytometric profiles of CCR8 cell surface expression on thymocyte subsets from <i>Ccr8</i>^<i>+/+</i> and <i>Ccr8</i>^<i>-/-</i> mice. Data are representative of two independent experiments, with a total of six mice per genotype. (C) Quantification of CCR8 Mean Fluorescence Intensities (MFI) in <i>Ccr8</i>^<i>+/+</i> to <i>Ccr8</i>^<i>-/-</i> thymocyte subsets, from data as in (B). Graph shows means + SD from one representative experiment with 3 mice per group; *<i>p</i> < 0.05, **<i>p</i> < 0.01, ***<i>p</i> < 0.001 (Unpaired two-tailed <i>t-test</i> with the Holm-Sidak multiple comparisons testing). (D and E) qRT-PCR analysis was used to quantify relative mRNA expression levels of the CCR8 ligands CCL1 and CCL8 in the indicated FACS-sorted thymic stromal cell subsets. Expression was normalized first to β-actin levels in each sample, and then between samples to expression in the mTEC^hi subset. Graph shows means + SEM compiled from two independent experiments, each with three technical replicates.