COVID-19, caused by SARS-CoV-2 virus, emerged as a pandemic disease posing a severe threat to global health. To date, sporadic studies have demonstrated that innate immune mechanisms, specifically neutrophilia, NETosis, and neutrophil-associated cytokine responses, are involved in COVID-19 pathogenesis; however, our understanding of the exact nature of this aspect of host–pathogen interaction is limited. Here, we present a detailed dissection of the features and functional profiles of neutrophils, dendritic cells, and monocytes in COVID-19. We portray the crucial role of neutrophils as drivers of hyperinflammation associated with COVID-19 disease via the shift towards their immature forms, enhanced degranulation, cytokine production, and augmented interferon responses. We demonstrate the impaired functionality of COVID-19 dendritic cells and monocytes, particularly their low expression of maturation markers, increased PD-L1 levels, and their inability to upregulate phenotype upon stimulation. In summary, our work highlights important data that prompt further research, as therapeutic targeting of neutrophils and their associated products may hold the potential to reduce the severity of COVID-19.

Neutrophils releasing neutrophil extracellular traps (NETs) infiltrate the pancreas prior to type 1 diabetes (T1D) onset; however, the precise nature of their contribution to disease remains poorly defined. To examine how NETs affect immune functions in T1D, we investigated NET composition and their effect on dendritic cells (DCs) and T lymphocytes in T1D children. We showed that T1D patient NET composition differs substantially from that of healthy donors and that the presence of T1D-NETs in a mixed peripheral blood mononuclear cell culture caused a strong shift toward IFNγ-producing T lymphocytes, mediated through activation of innate immunity cells in T1D samples. Importantly, in a monocyte-derived DC (moDC) culture, NETs induced cytokine production, phenotypic change and IFNγ-producing T cells only in samples from T1D patients but not in those from healthy donors. RNA-seq analysis revealed that T1D-NETs presence causes TGFβ downregulation and IFNα upregulation and creates pro-T1D signature in healthy moDCs.

Background: Common variable immunodeficiency disorder (CVID) is one of the most frequent inborn errors of immunity, Increased occurrence of malignancies, particularly lymphomas and gastric cancers, has long been noted among CVID patients. Multifactorial aetiology, including immune dysregulation, infections, chronic inflammation or genetic background, is suggested to contribute to tumour development. Here, we present the results of the first Czech nationwide study focused on epidemiology, immunology and genetic background in a cohort of CVID patients who also developed tumours. Methods: The cohort consisted of 295 CVID patients followed for 3070 patient/years. Standardized incidence ratio (SIR) was calculated to determine the risk of cancer, and Risk ratio (RR) was established to evaluate the significance of comorbidities. Moreover, immunophenotyping, including immunoglobulin levels and lymphocyte populations, was assessed. Finally, Whole exome sequencing (WES) was performed in all patients with lymphoma to investigate the genetic background. Results: Twenty-five malignancies were diagnosed in 22 patients in a cohort of 295 CVID patients. SIR was more than 6 times greater in comparison to the general population. The most common neoplasias were gastric cancers and lymphomas. History of Immune thrombocytopenic purpura (ITP) was established as a potential risk factor, with over 3 times higher risk of cancer development. The B cell count at diagnosis of lymphoma was reduced in the lymphoma group; moreover, post-treatment B and T cell lymphopenia, associated with poorer outcome, was found in a majority of the patients. Intriguingly, no NK cell depression was observed after the chemotherapy. WES revealed heterogeneous genetic background among CVID patients with tumours, identifying gene variants associated with primary immunodeficiencies (such as CTLA4, PIK3CD, PMS2) and/or increased cancer susceptibility (including BRCA1, RABEP1, EP300, KDM5A). Conclusions: The incidence of malignancy in our CVID cohort was found to be more than 6 times greater compared to the general population. Gastric cancers and lymphomas were the most frequently diagnosed tumours. ITP was identified as a risk factor for malignancy in CVID patients. WES analysis confirmed a wide genetic heterogeneity among CVID patients. The identified causative or modifying gene variants pointed to errors in mechanisms contributing to both immunodeficiency and malignancy.

MDSCs represent one of the key players mediating immunosuppression. These cells accumulate in the TME, lymphoid organs, and blood during tumor growth. Their mobilization was also reported after CY therapy. DNMTi 5AC has been intensively studied as an antitumor agent. In this study, we examined, using two different murine tumor models, the modulatory effects of 5AC on TU-MDSCs and CY-MDSCs tumor growth and CY therapy. Indeed, the percentage of MDSCs in the TME and spleens of 5AC-treated mice bearing TRAMP-C2 or TC-1/A9 tumors was found decreased. The changes in the MDSC percentage were accompanied by a decrease in the Arg-1 gene expression, both in the TME and spleens. CY treatment of the tumors resulted in additional MDSC accumulation in the TME and spleens. This accumulation was subsequently inhibited by 5AC treatment. A combination of CY with 5AC led to the highest tumor growth inhibition. Furthermore, in vitro cultivation of spleen MDSCs in the presence of 5AC reduced the percentage of MDSCs. This reduction was associated with an increased percentage of CD11c⁺ and CD86⁺/MHCII⁺ cells. The observed modulatory effect on MDSCs correlated with a reduction of the Arg-1 gene expression, VEGF production, and loss of suppressive capacity. Similar, albeit weaker effects were observed when MDSCs from the spleens of tumor-bearing animals were cultivated with 5AC. Our findings indicate that beside the direct antitumor effect, 5AC can reduce the percentage of MDSCs accumulating in the TME and spleens during tumor growth and CY chemotherapy, which can be beneficial for the outcome of cancer therapy.