Infection with SARS-CoV-2 can lead to Coronavirus disease-2019 (COVID-19) and result in severe acute respiratory distress syndrome (ARDS). Recent reports indicate an increased rate of fungal coinfections during COVID-19. With incomplete understanding of the pathogenesis and without any causative therapy available, secondary infections may be detrimental to the prognosis. We monitored 11 COVID-19 patients with ARDS for their immune phenotype, plasma cytokines, and clinical parameters on the day of ICU admission and on day 4 and day 7 of their ICU stay. Whole blood stimulation assays with lipopolysaccharide (LPS), heat-killed Listeria monocytogenes (HKLM), Aspergillus fumigatus, and Candida albicans were used to mimic secondary infections, and changes in immune phenotype and cytokine release were assessed. COVID-19 patients displayed an immune phenotype characterized by increased HLA-DR+CD38+ and PD-1+ CD4+ and CD8+ T cells, and elevated CD8+CD244+ lymphocytes, compared to healthy controls. Monocyte activation markers and cytokines IL-6, IL-8, TNF, IL-10, and sIL2Rα were elevated, corresponding to monocyte activation syndrome, while IL-1β levels were low. LPS, HKLM and Aspergillus fumigatus antigen stimulation provoked an immune response that did not differ between COVID-19 patients and healthy controls, while COVID-19 patients showed an attenuated monocyte CD80 upregulation and abrogated release of IL-6, TNF, IL-1α, and IL-1β toward Candida albicans. This study adds further detail to the characterization of the immune response in critically ill COVID-19 patients and hints at an increased susceptibility for Candida albicans infection.

Secondary infections have been shown to complicate the clinical course and worsen the outcome of critically ill patients. Severe Coronavirus Disease 2019 (COVID-19) may be accompanied by a pronounced cytokine release, and immune competence of these patients towards most pathogenic antigens remains uncompromised early in the disease. Patients with bacterial sepsis also exhibit excessive cytokine release with systemic hyper-inflammation, however, typically followed by an anti-inflammatory phase, causing immune paralysis. In a second hit immune response model, leukocyte activation capacity of severely ill patients with pneumonia caused by SARS-CoV-2 or by bacteria were compared upon ICU admission and at days 4 and 7 of the ICU stay. Blood cell count and release of the pro-inflammatory cytokines IL-2, IFNγ and TNF were assessed after whole-blood incubation with the potent immune stimulus pokeweed mitogen (PWM). For comparison, patients with bacterial sepsis not originating from pneumonia, and healthy volunteers were included. Lymphopenia and granulocytosis were less pronounced in COVID-19 patients compared to bacterial sepsis patients. After PWM stimulation, COVID-19 patients showed a reduced release of IFNγ, while IL-2 levels were found similar and TNF levels were increased compared to healthy controls. Interestingly, concentrations of all three cytokines were significantly higher in samples from COVID-19 patients compared to samples from patients with bacterial infection. This fundamental difference in immune competence during a second hit between COVID-19 and sepsis patients may have implications for the selection of immune suppressive or enhancing therapies in personalized medicine.

A prolonged stress burden is known to hamper the efficiency of both the innate and the adaptive immune systems and to attenuate the stress responses by the catecholaminergic and endocannabinoid (EC) systems. Key mechanisms of innate immunity are the eradication of pathogens through phagocytosis and the respiratory burst. We tested the concentration-dependent, spontaneous and stimulated (via TNFα and N-formylmethionine-leucyl-phenylalanine) release of reactive oxygen species (ROS) by human polymorphonuclear leukocytes (PMNs) in vitro in response to norepinephrine (NE) and AM1241, a pharmacological ligand for the EC receptor CB2. We evaluated phagocytosis of Dectin-1 ligating zymosan particles and tested the cytokine response against Candida antigen in an in vitro cytokine release assay. Increasing concentrations of NE did not affect phagocytosis, yet stimulated ROS release was attenuated gradually reaching maximum suppression at 500 nM. Adrenergic receptor (AR) mechanisms using non-AR-selective (labetalol) as well as specific α-(prazosin) and β-(propranolol) receptor antagonists were tested. Results show that only labetalol and propranolol were able to recuperate cytotoxicity in the presence of NE, evidencing a β-receptor-mediated effect. The CB2 agonist, AM1241, inhibited phagocytosis at 10 µM and spontaneous peroxide release by PMNs. Use of the inverse CB2 receptor agonist SR144528 led to partial recuperation of ROS production, confirming the functional role of CB2. Additionally, AM1241 delayed early activation of monocytes and induced suppression of IL-2 and IL-6 levels in response to Candida via lower activity of mammalian target of rapamycin (mTOR). These findings provide new insights into key mechanisms of innate immunity under stressful conditions where ligands to the sympatho-adrenergic and EC system are released.

Eosinophils (EOS) quantity, active state, peroxidase activity (POX), and HLA-DR expression in bone marrow of 176 Auto-Immune-Related Hematocytopenia (AIRH) patients were analyzed. Immunofluorescent staining (IF) is performed to observe the expression of immunizing molecules on EOS. In serum of AIRH patients the levels of IL-4, IL-5, IL-6, IL-12, IL-17, and IFN- γ were increased but there was no significance on IL-2 level. In marrow of AIRH, activated EOS expressed POX, and other molecules, it played various cell-mediated immunity injury roles to hemocyte. EOS might be possessed with multiple immunological fuctions, it playes an important immune effect in AIRH autoimmune pathological processes.

Because of environmental pollution more and more people are suffered with auto-immuno-related hematocytopenia (AIRH). Serum IL-12, IL-17, and IFN-γ levels were detected by ELISA and lymphocyte subsets were analyzed by flow cytometry. Peroxidase (POX) and HLA-DR of immune cells were detected by cytochemical and immunochemical staining. Cells expressing anti-human IgG, FcγR II, MR, and other molecules in HI were detected by immunofluorescence. Serum IL-12, IL-17, and IFN-γ levels of patients were significantly higher than control group. Lymphocyte subsets of patients showed that the percentages of CD19+ B cells and CD3+ CD8+ T cell in peripheral blood were both significantly elevated. HI were mainly classified into three types, in these three types of hematopoietic cells island, peroxidase, and HLA-DR expression varied. Hematopoietic cells with pathological changes expressed anti-human IgG. The immunocytes with different levels of immunomolecules adhered captured and devoured abnormal hematopoietic cells. Immune cells expressed IL-12, IL-17A, and IL-17RA, leading to inflammatory injury of hematopoietic cells. HI destroys cells which connect auto-antibodies. Immune cells in HI express a variety of immune molecules, promote cell immune responses, and amplify the inflammatory reaction by ADCC effect or phagocytosis. These ultimately destruct directly and damage indirectly hematopoietic cells.