Transwell chemotaxis of E14.5 fetal thymocytes to chemokines. (A) Freshly isolated E14.5 fetal thymocytes were examined for chemotactic responses to indicated recombinant chemokines (100 nM) in 6 hours. The responses are expressed as percentage of migrated cells within total input cells. (B-C) A low concentration (20 nM) of chemokines was used for the 6-hour transwell chemotaxis of E14.5 fetal thymocytes. Migrated cells were stained for CD44 and CD25 to identify the subset of DN1 and DN2 thymocyte subpopulations in panel B. Means and SEs are indicated. Numbers next to bars indicate the numbers of independent experiments. Asterisks denote significant responses (*P < .05; **P < .01; ***P < .001).