Open Access

Background: Newborns are prone to infections, which are independent predictors of neonatal mortality and morbidity. Neutrophil extracellular traps (NETs) are structures composed of chromatin and antimicrobial molecules that capture and kill pathogens. NETs may play an important role in the innate immune system and, thus, might be associated with impaired neonatal immune function. Objectives: This study aimed to compare NET formation between term neonates and healthy adults. We additionally investigated the effects of gestational age, birth weight, mode of delivery, gender, and perinatal infections. Methods: We collected cord blood from 57 term infants (mean gestational age, 39.1 weeks) and 9 late preterm infants (35 weeks), and peripheral blood from 18 healthy adult donors. Neutrophils were isolated, and then NET formation was induced using three different stimulants: N-formylmethionine-leucyl-phenylalanine, phorbol 12-myristate 13-acetate (PMA), or lipopolysaccharide. NETs were immunohistochemically stained and analyzed with regard to NET percentage and NET area. Results: With all three stimuli, healthy term infants showed a lower NET percentage than the adult control group (p < 0.0001 each). The groups also differed in NET area, but the significance level was lower. Following PMA stimulation, we observed greater reductions in NET percentage and NET area in preterm than term infants. Conclusions: The lower NET formation observed in term infants compared to adults likely contributes to the reduced neonatal immune response. NET formation appeared to be even further decreased in late preterm neonates. There remains a need for further investigations of NET formation in more immature preterm infants.

Background: Granulocytes and monocytes are the first cells to invade the brain post stroke and are also being discussed as important cells in early neuroinflammation after seizures. We aimed at understanding disease specific and common pathways of brain-immune-endocrine-interactions and compared immune alterations induced by stroke and seizures. Therefore, we compared granulocytic and monocytic subtypes between diseases and investigated inflammatory mediators. We additionally investigated if seizure type determines immunologic alterations. Material and Methods: We included 31 patients with acute seizures, 17 with acute stroke and two control cohorts. Immune cells were characterized by flow cytometry from blood samples obtained on admission to the hospital and the following morning. (i) Monocytes subpopulations were defined as classical (CD14++CD16−), (ii) intermediate (CD14++CD16+), and (iii) non-classical monocytes (CD14dimCD16+), while granulocyte subsets were characterized as (i) “classical granulocytes” (CD16++CD62L+), (ii) pro-inflammatory (CD16dimCD62L+), and (iii) anti-inflammatory granulocytes (CD16++CD62L−). Stroke patient's blood was additionally drawn on days 3 and 5. Cerebrospinal fluid mitochondrial DNA was quantified by real-time PCR. Plasma High-Mobility-Group-Protein-B1, metanephrine, and normetanephrine were measured by ELISA. Results: HLA-DR expression on monocytes and their subpopulations (classical, intermediate, and non-classical monocytes) was reduced after stroke or seizures. Expression of CD32 was increased on monocytes and subtypes in epilepsy patients, partly similar to stroke. CD32 and CD11b regulation on granulocytes and subpopulations (classical, anti-inflammatory, pro-inflammatory granulocytes) was more pronounced after stroke compared to seizures. On admission, normetanephrine was upregulated in seizures, arguing for the sympathetic nervous system as inducer of immune alterations similar to stroke. Compared to partial seizures, immunologic changes were more pronounced in generalized tonic-clonic seizures. Conclusion: Seizures lead to immune alterations within the immediate postictal period similar but not identical to stroke. The type of seizures determines the extent of immune alterations.

We performed this cohort study to test whether further analysis of intrathecal inflammation can be omitted if the free light chain kappa (FLCκ) quotient is within the reference range in the corresponding quotient diagram. FLCκ concentrations were measured in serum and cerebrospinal fluid (CSF) samples. The intrathecal fraction (IF) of FLCκ was calculated in relation to the hyperbolic reference range. 679 patient samples were used as a discovery cohort (DC). The sensitivity and negative predictive value (NPV) of the FLCκ-IF for the detection of an intrathecal humoral immune response (CSF-specific OCB and/or IF IgG/A/M > 0%) was determined. Based on these data, a diagnostic algorithm was developed and prospectively validated in an independent validation cohort (VC, n = 278). The sensitivity of the FLCκ-IF was 98% in the DC and 97% in the VC with a corresponding NPV of 99%. The use of the FLCκ-IF as a first line analysis would have reduced the Ig and OCB analysis by 62% in the DC and 74% in the VC. The absence of a FLCκ-IF predicts the absence of a humoral intrathecal immune response with a very high NPV of 99%. Thus, integration of our proposed algorithm into routine CSF laboratory analysis could help to reduce analytical efforts.

Background: Stroke patients are at risk of acquiring secondary infections due to stroke-induced immune suppression (SIIS). Immunosuppressive cells comprise myeloid-derived suppressor cells (MDSCs) and immunosuppressive interleukin 10 (IL-10)-producing monocytes. MDSCs represent a small but heterogeneous population of monocytic, polymorphonuclear (or granulocytic), and early progenitor cells (“early” MDSC), which can expand extensively in pathophysiological conditions. MDSCs have been shown to exert strong immune-suppressive effects. The role of IL-10-producing immunosuppressive monocytes after stroke has not been investigated, but monocytes are impaired in oxidative burst and downregulate human leukocyte antigen—DR isotype (HLA-DR) on the cell surface. Objectives: The objective of this work was to investigate the regulation and function of MDSCs as well as the immunosuppressive IL-10-producing monocytes in experimental and human stroke. Methods: This longitudinal, monocentric, non-interventional prospective explorative study used multicolor flow cytometry to identify MDSC subpopulations and IL-10 expression in monocytes in the peripheral blood of 19 healthy controls and 27 patients on days 1, 3, and 5 post-stroke. Quantification of intracellular STAT3p and Arginase-1 by geometric mean fluorescence intensity was used to assess the functionality of MDSCs. In experimental stroke induced by electrocoagulation in middle-aged mice, monocytic (CD11b+Ly6G−Ly6Chigh) and polymorphonuclear (CD11b+Ly6G+Ly6Clow) MDSCs in the spleen were analyzed by flow cytometry. Results: Compared to the controls, stroke patients showed a relative increase in monocytic MDSCs (percentage of CD11b+ cells) in whole blood without evidence for an altered function. The other MDSC subgroups did not differ from the control. Also, in experimental stroke, monocytic, and in addition, polymorphonuclear MDSCs were increased. The numbers of IL-10-positive monocytes did not differ between the patients and controls. However, we provide a new insight into monocytic function post-stroke since we can report that a differential regulation of HLA-DR and PD-L1 was found depending on the IL-10 production of monocytes. IL-10-positive monocytes are more activated post-stroke, as indicated by their increased HLA-DR expression. Conclusions: MDSC and IL-10+ monocytes can induce immunosuppression within days after stroke.