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Introduction and ObjectivesMyeloid-derived suppressor cells (MDSCs) are immature cells with immunosuppressive properties, divided into polymorphonuclear (PMN-) and monocytic (M-) subpopulations. Based on a limited number of disease-specific studies, they appear to be involved in a wide spectrum of lung diseases. We aimed to standardise a simple measuring protocol of MDSCs in the lungs and the systemic circulation and to comparatively investigate their differences among distinct lung diseases.MethodsIn 16 patients with lung diseases, MDSCs were measured in peripheral blood (PB) and bronchoalveolar lavage (BAL) via flow cytometry and immunophenotypically defined as CD45+CD3−CD19−CD20−CD56−CD16−HLA-DR−CD33+CD11b+CD15+Lox-1+ PMN-MDSCs and CD45+CD3−CD19−CD20−CD56−CD16−HLA-DR−CD33+CD11b+CD14+ M-MDSCs, as shown in figure 1a. Total MDSCs were calculated as the sum of the two subpopulations. Their suppressive character was confirmed via T-cell suppression assay. BAL cell populations were also defined. Further clinical and laboratory data were collected, including diagnosis, stage of disease, findings from microbiological, cytological, and histological examinations, disease course, and end outcomes. The data were analysed with the non-parametric Wilcoxon signed ranks test for paired samples and the Kruskal-Wallis test for comparison between multiple groups.ResultsOur study population included 4 patients with bronchiectasis, 6 patients with lung cancer, and 6 patients with interstitial lung diseases (ILD). MDSCs from all study subgroups showed normal capacity to suppress T cells. All MDSC subsets, including total MDSCs, M-MDSCs, and PMN-MDSCs, were statistically significantly increased in BAL compared to PB, as depicted in figure 1b, indicating the lung accumulation of these cells (p-value: <0.05 in all disease groups). Interestingly, total MDSCs in the BAL were statistically significantly differentiated between the three patient groups, as depicted in figure 1c, with the group of patients with ILD presenting the higher counts (p-value: 0.001).Abstract P251 Figure 1[Image Omitted. See PDF.]ConclusionsOur preliminary data show for the first time that MDSCs could potentially be used as differential diagnostic biomarkers in lung diseases. Additional data are needed to develop disease- and sample-specific reference values of MDSCs and further investigate their quantitative alterations in different entities.

Introduction and ObjectivesMyeloid-derived suppressor cells (MDSCs) are immature cells of the myeloid lineage with immunosuppressive properties, divided into polymorphonuclear and monocytic subpopulations, and are commonly involved in chronic inflammatory diseases. We aimed to systematically review the literature to assess the quantitative and qualitative alterations of MDSCs and their involvement in allergic airway diseases, i.e. asthma and allergic rhinitis.MethodsThe systematic review protocol was registered in PROSPERO, and the PRISMA guidelines for systematic reviews were followed. The databases MEDLINE via PubMed, Embase, and Scopus were systematically searched for original research studies involving the measurement of human MDSCs in allergic airway diseases by the end of 2024. A narrative synthesis of the extracted data from the included studies was performed.ResultsAmong a total of 429 records screened, 8 studies were considered eligible to be included in the review. The studies were run from 2011 to 2021 and cumulatively included 212 patients with asthma and 90 patients with allergic rhinitis. Healthy controls (cumulatively 203) were included in 7 studies, while 4 studies also included patients with other respiratory diseases for comparison, i.e. chronic obstructive pulmonary disease (35 patients), pneumonia (65 patients), and respiratory viral infections (27 patients). Out of 6 studies about asthma, MDSC counts were found either increased or increasing after allergen challenge in bronchoalveolar lavage (2 studies) and in peripheral blood mononuclear cells (3 studies), while the monocytic MDSC subpopulation was found downregulated in isolated white blood cells in only 1 study. The 2 studies about allergic rhinitis used diverse experimental set-ups and were not comparable.ConclusionsIncreased counts of MDSCs are mostly found in asthma, pointing towards the role of these immunomodulatory cells in its pathogenesis, despite the heterogeneity of the methodology among the different studies. Further research and harmonisation of the markers and techniques for the identification of MDSCs is needed, as they may be used as novel biomarkers and therapeutic targets in these disease entities.