SLPI and bronchiolitis obliterans syndrome: Our recent finding of decreased levels of the epithelial cell product secretory leukocyte proteinase inhibitor (SLPI) in the BAL fluid of lung allograft recipients with bronchiolitis obliterans supports this model.20 In addition, our study showed that the antimicrobial peptide LL-37 is elevated in the BAL fluid of allograft recipients with chronic dysfunction.20 As well as being an antimicrobial, LL-37 has been shown to interact with DC, and CD86 expression following LL-37 treatment has been shown to be increased in a dose-dependent manner.21