Background: CLAD (Chronic Lung Allograft Dysfunction) remains a serious complication following lung transplantation. Some evidence show that a fraction of ECP-treated patients improve/stabilize their graft function. In spite of that, data concerning molecular mechanism are still lacking.

Aim: Assess whether ECP effects are mediated by PBMCs modulation in term of miRNAs expression and growth factors/cytokines release.

Methods: PBMCs from leuko-apheresis from 12 o-CLAD patients, at time 0 and 6-months (X cycles), were cultured for 48h +/- PHA (10 ug/ml) or LPS (2 ug/ml). Expression levels of miR-146a-5p, miR-155-5p, miR-31-5p, miR181a-5p, miR-142-3p, miR-16-5p and miR-23b-5p in PBMCs-exosomes were evaluated by qRT-PCR and different cytokines levels were assessed on cell supernatants by ELISA.

Results: After 6 month-ECP we observed: miR-142-3p down-regulation (p=0.054), also after LPS stimulation (p=0.05); miR-146a-5p up-regulation in cells stimulated with LPS (p=0.02); CTGF levels that significantly decreased in PBMCs supernatant (p=0.04).

Conclusion: We observed that the up-regulation of miR-146a-5p, we previously observed in serum of ECP-treated patients, is due to its release by PBMCs. This miRNA is known to regulate immune system and tolerance via T regulatory cells modulation. miR-142-3p plays a role in Treg function modulation as reported by Huang B et al (EMBO reports (2009) 10, 180?185) and in particular, its down-regulation confers suppressor function on Treg cells. Interestingly, a significant decrease in CTGF release has been observed, this data if confirmed in larger cohort, suggest a possible interference of ECP also in graft fibrogenesis.