Figure 2.

Reduced thymic output and lymphopenia-induced homeostatic expansion of peripheral T cells in Ccr2^−/− mice. Single cell suspensions were prepared from the lymph node (LN) and spleen (SPL) of wild-type (WT) and Ccr2 knockout (KO) mice at 6 and 13 weeks of age and analyzed by flow cytometry. (A) Representative dot plots showing EGFP⁺ RTEs in CD4⁺ and CD8⁺ T cells from 6-week-old mice. (B) The percentage of RTEs in the peripheral CD4⁺ and CD8⁺ T cells in 6- and 13-week-old mice. Data are presented as mean ± SD with at least 10 mice for each group. (C) The absolute numbers of total and CD4⁺ and CD8⁺ RTEs in the SPL and LNs (axillary + inguinal + mesentery). (D) CD62L and CD44 staining for splenic CD4⁺ and CD8⁺ T cells in 6- and 13-week-old mice. The slight different gating for cells at different ages were based on the appearance of distinct populations under specific instrument settings. (E) Percentage of the CD62L^hiCD44^lo (naive), CD62L^loCD44^hi (activated), and CD62L^hiCD44^hi (memory) cells among CD4⁺ and CD8⁺ T cells. Data are presented as mean ± SEM with at least nine mice for each group. (F) Lethally irradiated mice were reconstituted with CD45.1⁺ WT and CD45.2⁺ KO bone marrow cells mixed at a ratio of 4:1. CD62L and CD44 expression by splenic CD4⁺ and CD8⁺ T cells were analyzed by gating on the CD45.1⁺ or CD45.2⁺ population in the recipient mice. Representative dot plots are shown out of two independent experiments with a total of nine mice. Statistical differences were determined by the Student’s t test. *p < 0.05, **p < 0.01, ***p < 0.001.