C5AR1 and bronchiolitis obliterans syndrome: Interestingly, fMLP elevated the expression of CCR8 (7.2% ± 2.9 vs. 13.8% ± 6.2) and XCR1 (3.9% ± 4.3 vs. 16.3% ± 15.7) on basophils in the BO group; however, the C5a stimulation increased the frequency of XCR1+ (12.8% ± 12.4) but not CCR8+ cells (Figure 3B).