Elevated mRNA levels of CTLA-4, FoxP3, and granzyme B in BAL, but not in blood, during acute rejection of lung allografts.

Introduction: Regulatory T cells (Tregs) have been related to acute rejection as have the cytotoxic T cells, their immunological counterpart. High expression of cytotoxic markers has been related to acute rejection incidents following both kidney and intestine transplantation, while the correlation between FoxP3 expression and acute rejection is still being debated. Some studies have been performed on blood samples from lung-transplanted patients, while others have investigated the local immune response in the lungs by analysing broncho-alveolar-lavage (BAL) fluids or biopsies. Biopsies are considered the gold standard in diagnosis of acute rejection. Aim: The aim was to measure the expression of both Treg (FoxP3, CD25 and CTLA-4) and cytotoxic (granzyme B, granulysin, and perforin) markers in BAL and blood samples from lung-transplanted patients to investigate the possible relation of expression and acute rejection incidents in order to develop a non-invasive diagnostic method for acute rejection. Materials and methods: 24 lung-transplanted patients were included in this 6-month cross-section study. BAL and blood samples were analysed for FoxP3, CD25, CTLA-4, granzyme B, granulysin, perforin, CD4 and CD8 mRNA by QRT-PCR with glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as primary reference. Results: We demonstrate that the mRNA levels in BAL relative to GAPDH of nearly all markers are elevated during acute rejection; CTLA-4, FoxP3, and granzyme B significantly, while a strong tendency is seen among the others. No significant differences were detected in blood. Conclusion: CTLA-4, FoxP3 and Granzyme B mRNA levels are elevated during acute rejection in BAL, but not in blood, following lung transplantation, indicating that evaluation of Treg and cytotoxic marker expression in BAL can be used in the assessment of allograft rejection state.