Cellular immune surveillance of central nervous system bypasses blood-brain barrier and blood-cerebrospinal-fluid barrier: Revealed with the New Marburg cerebrospinal-fluid model in healthy humans

Prospective Molecular Targets for Natural Killer Cell Immunotherapy against Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most common type of primary malignant brain tumor and has a dismal overall survival rate. To date, no GBM therapy has yielded successful results in survival for patients beyond baseline surgical resection, radiation, and chemotherapy. Immunotherapy has taken the oncology world by storm in recent years and there has been movement from researchers to implement the immunotherapy revolution into GBM treatment. Natural killer (NK) cell-based immunotherapies are a rising candidate to treat GBM from multiple therapeutic vantage points: monoclonal antibody therapy targeting tumor-associated antigens (TAAs), immune checkpoint inhibitors, CAR-NK cell therapy, Bi-specific killer cell engagers (BiKEs), and more. NK therapies often focus on tumor antigens for targeting. Here, we reviewed some common targets analyzed in the fight for GBM immunotherapy relevant to NK cells: EGFR, HER2, CD155, and IL-13Rα2. We further propose investigating the Lectin-like Transcript 1 (LLT1) and cell surface proliferating cell nuclear antigen (csPCNA) as targets for NK cell-based immunotherapy.

Analysis of cerebrospinal fluid cells by flow cytometry: Comparison to conventional cytology

AIMS

This study compared the results obtained by basic immunophenotyping of cerebrospinal fluid (CSF) cells by flow cytometry (FC) to the results of conventional cytology and evaluated the possibility of detailed analyses of CSF B-cell subpopulations.

METHODS

Samples from 42 patients were examined by conventional cytology (native and/or pre-centrifuged CSF) and FC. The results from 15 patients without evidence of organic neurological disease were used to estimate reference ranges.

RESULTS

Pre-centrifugated CSF had significantly higher cell yield on the cytologic slide, but cell subpopulation percentages were altered; the percentage of lymphocytes was significantly higher and monocytes significantly lower compared to both native CSF slides and FC. The percentage of granulocytes was higher in FC compared to cytology. For leukocyte count, the following reference ranges were estimated for Fuchs-Rosenthal chamber (FR) counting and FC, respectively: leukocytes ≤4.7/μL and ≤2.5/μL, lymphocytes ≤4.1/μL and ≤1.8/μL, monocytes ≤1.2/μL and ≤0.9/μL, and granulocytes 0/μL and ≤0.2/μL. The following reference ranges were estimated for basic subpopulations: T-lymphocytes 84.1 - 100%, B lymphocytes 0.0 - 1.5%, NK cells 0.0 - 6.3%, NKT cells 0 - 9.5%, and CD3+CD4+/CD3+CD8+ 0.8 - 4.9. Using a volume of 1.2-2.4 mL, the number of B lymphocytes was too low (<20) in samples with ≤2.7 cells/μL in the FR.

CONCLUSIONS

Even normal CSF samples are amenable to basic mononuclear cell subpopulation analysis by FC. However, analysis of the B-cell subpopulations requires either a larger sample volume or selection of samples with ≥ 3 cells/μL.

Major Differences in Lymphocyte Subpopulations Between Cerebrospinal Fluid and Peripheral Blood in Non-Hodgkin Lymphoma Without Leptomeningeal Involvement: Flow Cytometry Evidence of a Cerebral Lymphatic System

Cerebrospinal fluid (CSF) flow cytometry has a crucial role in the diagnosis of leptomeningeal disease in onco-hematology. This report describes the flow cytometry characterization of 138 CSF samples from patients affected by non-Hodgkin lymphoma, negative for disease infiltration. The aim was to focus on the CSF non-neoplastic population, to compare the cellular composition of the CSF with paired peripheral blood samples and to document the feasibility of flow cytometry in hypocellular samples. Despite the extremely low cell count (1 cell/µl, range 1.0-35) the study was successfully conducted in 95% of the samples. T lymphocytes were the most abundant subset in CSF (77%; range 20-100%) with a predominance of CD4-positive over CD8-positive T cells (CD4/CD8 ratio = 2) together with a minority of monocytes (15%; range 0-70%). No B cells were identified in 90% of samples. Of relevance, a normal, non-clonal B-cell population was documented in 5/7 (71%) patients with primary central nervous system lymphoma at diagnosis (p<0.0001), suggesting a possible involvement of blood-brain barrier cell permeability in the pathogenesis of cerebral B-cell lymphomas. The highly significant differences between CSF and paired peripheral blood lymphoid phenotype (p<0.0001) confirms the existence of an active mechanism of lymphoid migration through the meninges.

Generation of a Model to Predict Differentiation and Migration of Lymphocyte Subsets under Homeostatic and CNS Autoinflammatory Conditions

The central nervous system (CNS) is an immune-privileged compartment that is separated from the circulating blood and the peripheral organs by the blood–brain and the blood–cerebrospinal fluid (CSF) barriers. Transmigration of lymphocyte subsets across these barriers and their activation/differentiation within the periphery and intrathecal compartments in health and autoinflammatory CNS disease are complex. Mathematical models are warranted that qualitatively and quantitatively predict the distribution and differentiation stages of lymphocyte subsets in the blood and CSF. Here, we propose a probabilistic mathematical model that (i) correctly reproduces acquired data on location and differentiation states of distinct lymphocyte subsets under homeostatic and neuroinflammatory conditions, (ii) provides a quantitative assessment of differentiation and transmigration rates under these conditions, (iii) correctly predicts the qualitative behavior of immune-modulating therapies, (iv) and enables simulation-based prediction of distribution and differentiation stages of lymphocyte subsets in the case of limited access to biomaterial. Taken together, this model might reduce future measurements in the CSF compartment and allows for the assessment of the effectiveness of different immune-modulating therapies.

Human dorsal root ganglion pulsed radiofrequency treatment modulates cerebrospinal fluid lymphocytes and neuroinflammatory markers in chronic radicular pain

Radicular pain is a common cause of disability. Traditionally treatment has been either epidural steroid injection providing short-term relief or surgery with associated complications. Pulsed radiofrequency (PRF) applied to the dorsal root ganglion (DRG) is a minimally invasive day-care treatment, which is gaining significant clinical acceptance in a selective group of patients with pure radicular pain. Greater insights into the immunomodulatory effects of this procedure may help to further optimise its application and find alternative treatment options. We have examined it's effect on lymphocyte frequencies and secreted inflammatory markers in the cerebrospinal fluid (CSF) and correlated this with clinical outcome to identify clinical markers of chronic radicular pain. Ten patients were recruited for the study. CSF lymphocyte frequencies and levels of cytokines, chemokines and growth factors were quantified using flow cytometry and enzyme-linked immunosorbent assay (ELISA), respectively. Clinical assessment utilised Brief Pain Inventory scores. Nine out of ten patients (90%) demonstrated significant reduction in pain severity (p = 0.0007) and pain interference scores (p = 0.0015) three months post-treatment. Our data revealed significant reductions in CD56⁺, CD3^-, NK cell frequencies (p = 0.03) and IFN-γ levels (p = 0.03) in treatment responders, while CD8⁺ T cell frequencies (p = 0.02) and IL-6 levels were increased (p = 0.05). IL-17 inversely correlated with post-treatment pain severity score (p = 0.01) and pre and post-treatment pain interference scores (p = 0.03, p = 0.01). These results support the concept that chronic radicular pain is a centrally mediated neuroimmune phenomenon and the mechanism of action of DRG PRF treatment is immunomodulatory.

The development of dendritic cell vaccine-based immunotherapies for glioblastoma

In this review, we focus on the biologic advantages of dendritic cell-based vaccinations as a therapeutic strategy for cancer as well as preclinical and emerging clinical data associated with such approaches for glioblastoma patients.

Type I/II Interferon Balance in the Regulation of Brain Physiology and Pathology

Recent findings have revealed distinct roles for type I and II interferons (IFN-I and IFN-γ) in the recruitment of immune cells to the central nervous system (CNS) and highlighted the importance of this process for brain maintenance and protection/repair. Furthermore, manipulation of IFN-I and IFN-γ pathways in pathological contexts has yielded conflicting results. We discuss these findings, focusing on two distinct conditions; relapsing remitting multiple sclerosis (RRMS) and brain aging. Using these examples, we propose that regulation of immune cell entry to the CNS is a mechanism through which interaction between IFN-I and -II can affect brain function from its anatomical borders. Deviation from homeostatic IFN-I/-II balance may contribute to distinct brain pathologies, resulting from either insufficient immune surveillance of the CNS and loss of immune-dependent protection, or overwhelming leukocyte entry and immune-mediated destruction.

Novel flow cytometric analysis of the blood-brain barrier

The blood-brain barrier (BBB) is primarily comprised of brain microvascular endothelial cells (BMVEC) and astrocytes and serves as a physical and chemical barrier that separates the periphery from the brain. We describe a flow cytometric method using our in vitro model of the human BBB to characterize BMVEC surface junctional proteins critical for maintenance of barrier function, cell viability, and leukocyte adhesion. For this methodology, BMVEC are cocultured with astrocytes in a transwell tissue culture insert to establish the barrier, after which time the BBB are treated with specific agents, and the BMVEC collected for flow cytometric analyses. We use a standard and optimized method to recover the BMVEC from the coculture model that maintains junctional protein expression and cell viability. A novel leukocyte adhesion assay enables a quantitative analysis of peripheral blood mononuclear cell (PBMC) interactions with the BMVEC and can be used to assess the adhesion of many cell types to the BBB. Furthermore, this method enables the concomitant analysis of a large number of adhesion molecules and tight junction proteins on both the BMVEC and adherent PBMC under homeostatic and pathologic conditions. Flow cytometry is an extremely powerful tool, and this technique can also be applied to assess variables not performed in this study, including cell cycle progression, and calcium flux.