The Treg population in the lungs of chimeric mice (CCR7-/-→WT) was also increased compared with WT controls (WT→WT), an effect previously observed in BLM-treated CCR7-/- mice, and Tregs were present in the LNs of CCR7-/- chimeric mice 21 days after BLM injection challenge. Here, CCR7 is linked to Bloom syndrome.