TY - JOUR T1 - Identification of PD-L2 on macrophages in lung cancer milieu- pilot study JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.congress-2020.1767 VL - 56 IS - suppl 64 SP - 1767 AU - Iwona Kwiecień AU - Elżbieta Rutkowska AU - Małgorzata Polubiec-Kownacka AU - Piotr Rzepecki AU - Joanna Domagała-Kulawik Y1 - 2020/09/07 UR - http://erj.ersjournals.com/content/56/suppl_64/1767.abstract N2 - The efficacy of immune checkpoint inhibitors remains unexpected and in some patients the resistance to anti- PD-1, PD-L1 agents is observed. Possible explanation is may be PD-L2 activity. The ligands PD-L1 and PD-L2 are present on cancer cells but not-without significance- on macrophages (AMs) contributing to the immune-suppressive tumor microenvironment.The aim of this study was to evaluate PD-L2 expression on AMs in the bronchoalveolar lavage fluid (BALF) from lung affected by cancer (cBALF) and healthy lung (hBALF) in relation to PD-L1 AMs and PD-1 T lymphocytes.Patients with confirmed lung cancer were investigated. Flow cytometry method with a panel of monoclonal antibodies was used.We found that 100% of CD68+ macrophages from cBALF were PD-L1 and PD-L2 -positive. Unexpectedly, fluorescence minus one (FMO) PD-L1 and PD-L2 stained controls also showed strong autofluorescence and similar percentages of these cells fell within the same FLs channel that counted the anti-PD-L1 and PD-L2 stained population. The hBALF AMs exhibited similar PD-L1 and PD-L2 autofluorescence. The evaluation of expression of PD-1 on lymphocytes was much eastier: the median proportion of PD-1+ T cells was higher in cBALF then hlBALF and PB (33.3 vs. 17.9 vs 19.5%, p< 0.05). The geometric mean was higher in BALF then PB (1024 vs. 1196 vs. 408).Our study shows that macrophages autofluorescence did not allow to assess real expression of PD-L2 as well as PD-L1 on AMs. We conclude that the reported expression of PD-L1 and PD-L2 macrophages by flow cytometry should be combined with other qualitative methods to avoid false-positive results.FootnotesCite this article as: European Respiratory Journal 2020; 56: Suppl. 64, 1767.This abstract was presented at the 2020 ERS International Congress, in session “Respiratory viruses in the "pre COVID-19" era”.This is an ERS International Congress abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only). ER -