CCR7 expression on different thymocyte subpopulations. Thymocytes of adult C57BL/6 mice were stained with anti-CD4, anti-CD8, anti-CD24, and anti-CD69 antibodies. CCR7 was detected using a monoclonal antibody. (A) CCR7 expression on DP and SP thymocytes. Populations were gated based on the expression of CD4, CD8, and CD69 as indicated. Bright gray indicates CCR7; dark gray, isotype control. Numbers indicate the percentage of cells expressing CCR7 above the background level. (B) CCR7 expression on CD4 SP cells at different maturational stages. The analysis of CCR7 and CD24 coexpression on CD4⁺CD8⁻ cells allows the identification of 4 different subpopulations (i-iv). (C) Expression of CD69 on subpopulations i to iv depicted in panel B.