RT Journal Article SR Electronic T1 CD8+ T cells, dendritic cells, mast cells and FOXP3 in the lungs of patients with severe influenza A (H1N1) infection JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP P3505 VO 44 IS Suppl 58 A1 Monique Buttignol A1 Ruy Pires-Neto A1 Marina Ballarin A1 Marisa Dolhnikoff A1 Thais Mauad YR 2014 UL http://erj.ersjournals.com/content/44/Suppl_58/P3505.abstract AB Backgroud: Influenza A (H1N1) infection can induce acute respiratory distress syndrome (ARDS) in some patients. There are still few reports on the immunophenotype of the inflammatory cells present in lung infiltrates of patients that died due to H1N1 infection when compared to other causes of ARDS. Aim: Quantify CD8+T cells, Dendritic Cells (CD83), Natural Killer cells (NK–CD57), Mast Cells (chymase/tryptase) and Foxp3 regulatory T cells in the lungs of patients who died of H1N1. Methods: We analyzed autopsy lung tissue of 46 subjects (48±16 years, 55% male), divided in 3 groups according to cause of death: Control (non-pulmonary cause of death, n=16); ARDS (ARDS due to non viral infection, n=14) and H1N1 (H1N1 infection, n=16). Using immunohistochemistry and image analysis we quantified the density of CD8+T, chymase, tryptase, CD83, CD57+ and Foxp3 in the lung parenchyma. Data are expressed as cells/alveolar septum length (median [IQR]). Results: We found an increase of CD8+T cell density in H1N1 group when compared to ARDS and control groups (3.7[2.3] x 3.7[1.7] x 6.3[3.3] 103cels/μm, p=0.019). There was also an increase of CD83 cell density in H1N1 group compared to control (0.5[0.4] x 1.4[1] 103cels/μm, p=0.007). Finally, compared to ARDS group, H1N1 showed an increase of CD57 cell density (2[1] x 3.3[3] 103cels/μm, p=0.007). The expression of tryptase, chymase and Foxp3 was not different between groups. Conclusion: ARDS induced by H1N1 infection is associated with an inflammatory phenotype that is different from other causes of ARDS, with increased recruitment of cytotoxic, dendritic cells and NK cells to the lungs.