In vivo homing of CD4⁺ T cells to secondary lymphoid organs and on-site proliferation is CCR6 independent. (A) CMFDA-labeled WT and CMTMR-labeled CCR6-deficient CD4⁺ T cells (3 × 10⁶ each) were cotransferred into BALB/c-SCID mice and the percentage of donor cells in recipient spleens were determined at different times after cell transfer. (B) WT or CCR6-deficient CD4⁺ T cells transferred to BALB/c-SCID mice showed a similar proliferation ratio, as deduced from the sequential halving of the fluorescence intensity with each generation of CD4⁺ T cells in spleen and peripheral (PLN) and mesenteric (MLN) lymph nodes. Data are also shown from control transplants in which CFSE-labeled CD4⁺ T cells from BALB/c donors were transferred to BALB/c or BALB/c-SCID recipients. Plots represent CFSE-labeled cells recovered from 4 mice, 4 days after receiving a transplant of 10 × 10⁶ CFSE-labeled CD4⁺ T cells of the indicated genotypes. Similar results were obtained in 3 different experiments.