Mn administration promotes differentiation of the unique CCR6⁺CCR4⁺ donor Th17 cells after allogeneic BMT. Lethally irradiated B6 or B6D2F1 mice were transplanted with 4 × 10⁶ TCD-BM plus 4 × 10⁶ T cells from B6-background IL-17A−YFP fate mapping mice. Representative figure (A) of flow cytometric analysis 7 days after BMT is shown. The frequency (B) of YFP⁺ cells in CD4⁺ T-cell fraction in the spleen, lung, liver, and mesenteric lymph nodes (MLNs) from Syn controls (white bars), Mn-treated Syn mice (light gray bars), Allo controls (dark gray bars), and Mn-treated Allo mice (black bars) are shown as means ± standard error (SE) (n = 3 per group). (C) Representative dot plot shows 3 distinctive cell populations defined as YFP⁺CCR6⁺ (a), YFP⁺CCR6⁻ (b), and YFP⁻CCR6⁻ (c), respectively. (D) Messenger RNA expression in each cell fraction from Mn-treated allogeneic mice are shown as means ± SE. Frequencies (E) and numbers (F) of YFP⁺CCR6⁺ in the lung tissue 14 days after BMT are shown as means ± SE. Frequencies (G) and absolute numbers (H) of CCR6⁺ CD4⁺ YFP⁺ cells from the spleen, liver, and lung from Mn-treated allogeneic recipients on day 7 and day 14 after BMT are shown as means ± SE (n = 3). (I) Expression levels of Ccl20 messenger RNA in different tissues 14 days after BMT are shown. Representative data from 3 independent experiments (means ± SE) are shown. *P < .05; **P < .01.