Impaired calcium flux of CCR7-deficient thymocytes in response to CD3-ligation by cross-linking antibodies. (A) Wild-type (+/+) and CCR7-deficient (−/−) mice harbor comparable numbers of CD4⁺ SP and CD4⁺CD8⁺ DP thymocytes. Pseudocolor density plots are gated on living thymocytes according to forward and side scatter (FSC/SSC) profile. Numbers indicate the percentage of cells in the specified regions. (B) Impaired calcium flux of CCR7-deficient thymocytes in response to CD3 ligation by cross-linking antibodies. Pseudocolor density plots are gated on CD4⁺ SP or CD4⁺CD8⁺ DP thymocytes according to the gates depicted in (A). Black arrows indicate addition of CD3 and cross-linking antibodies. CCR7-deficient (−/−) CD4 SP thymocytes show reduced calcium flux in comparison to wild-type (+/+) as indicated by the red arrows. Note that a large fraction of the CCR7-deficient DP population remains mostly unresponsive (red arrowheads). Line graphs show median values of Fluo-4/Fura Red-ratio for wild-type (red) and CCR7-deficient thymocytes (blue). Data shown are representative of 3 independent experiments.