Brain volume change following anti-amyloid ß immunotherapy for Alzheimer's disease: amyloid-removal-related pseudo-atrophy.

Progressive cerebral volume loss on MRI is a hallmark of Alzheimer's disease and has been widely used as an outcome measure in clinical trials, with the prediction that disease-modifying treatments would slow loss. However, in trials of anti-amyloid immunotherapy, the participants who received treatment had excess volume loss. Explanations for this observation range from reduction of amyloid ß plaque burden and related inflammatory changes through to treatment-induced toxicity. The excess volume changes are characteristic of only those immunotherapies that achieve amyloid ß lowering; are compatible with plaque removal; and evidence to date does not suggest an association with harmful effects. Based on the current evidence, we suggest that these changes can be described as amyloid-removal-related pseudo-atrophy. Better understanding of the causes and consequences of these changes is important to enable informed decisions about treatments. Patient-level analyses of data from the trials are urgently needed, along with longitudinal follow-up and neuroimaging data, to determine the long-term trajectory of these volume changes and their clinical correlates. Post-mortem examination of cerebral tissue from treated patients and evaluation of potential correlation with antemortem neuroimaging findings are key priorities.

Decision making for health-related research outcomes that alter diagnosis: A model from paediatric brain tumours.

AIMS: The question of how to handle clinically actionable outcomes from retrospective research studies is poorly explored. In neuropathology, this problem is exacerbated by ongoing refinement in tumour classification. We sought to establish a disclosure threshold for potential revised diagnoses as determined by the neuro-oncology speciality. METHODS: As part of a previous research study, the diagnoses of 73 archival paediatric brain tumour samples were reclassified according to the WHO 2016 guidelines. To determine the disclosure threshold and clinical actionability of pathology-related findings, we conducted a result-evaluation approach within the ethical framework of BRAIN UK using a surrogate clinical multidisciplinary team (MDT) of neuro-oncology specialists. RESULTS: The MDT identified key determinants impacting decision-making, including anticipated changes to patient management, time elapsed since initial diagnosis, likelihood of the patient being alive and absence of additional samples since cohort inception. Ultimately, none of our research findings were considered clinically actionable, largely due to the cohort's historic archival and high-risk nature. From this experience, we developed a decision-making framework to determine if research findings indicating a change in diagnosis require reporting to the relevant clinical teams. CONCLUSIONS: Ethical issues relating to the use of archival tissue for research and the potential to identify actionable findings must be carefully considered. We have established a structured framework to assess the actionability of research data relating to patient diagnosis. While our specific findings are most applicable to the pathology of poor prognostic brain tumour groups in children, the model can be adapted to a range of disease settings, for example, other diseases where research is dependent on retrospective tissue cohorts, and research findings may have implications for patients and families, such as other tumour types, epilepsy-related pathology, genetic disorders and degenerative diseases.

Ultrafast Au(III)-Mediated Arylation of Cysteine.

Through mechanistic work and rational design, we have developed the fastest organometallic abiotic Cys bioconjugation. As a result, the developed organometallic Au(III) bioconjugation reagents enable selective labeling of Cys moieties down to picomolar concentrations and allow for the rapid construction of complex heterostructures from peptides, proteins, and oligonucleotides. This work showcases how organometallic chemistry can be interfaced with biomolecules and lead to a range of reactivities that are largely unmatched by classical organic chemistry tools.

Changes in the locus coeruleus during the course of Alzheimer's disease and their relationship to cortical pathology.

AIMS: In Alzheimer's disease (AD), the locus coeruleus (LC) undergoes early and extensive neuronal loss, preceded by abnormal intracellular tau aggregation, decades before the onset of clinical disease. Neuromelanin-sensitive MRI has been proposed as a method to image these changes during life. Surprisingly, human post-mortem studies have not examined how changes in LC during the course of the disease relate to cerebral pathology following the loss of the LC projection to the cortex. METHODS: Immunohistochemistry was used to examine markers for 4G8 (pan-Aß) and AT8 (ptau), LC integrity (neuromelanin, dopamine ß-hydroxylase [DßH], tyrosine hydroxylase [TH]) and microglia (Iba1, CD68, HLA-DR) in the LC and related temporal lobe pathology of 59 post-mortem brains grouped by disease severity determined by Braak stage (0-II, III-IV and V-VI). The inflammatory environment was assessed using multiplex assays. RESULTS: Changes in the LC with increasing Braak stage included increased neuronal loss (p < 0.001) and microglial Iba1 (p = 0.005) together with a reduction in neuromelanin (p < 0.001), DßH (p = 0.002) and TH (p = 0.041). Interestingly in LC, increased ptau and loss of neuromelanin were detected from Braak stage III-IV (p = 0.001). At Braak stage V/VI, the inflammatory environment was different in the LC vs TL, highlighting the anatomical heterogeneity of the inflammatory response. CONCLUSIONS: Here, we report the first quantification of neuromelanin during the course of AD and its relationship to AD pathology and neuroinflammation in the TL. Our findings of neuromelanin loss early in AD and before the neuroinflammatory reaction support the use of neuromelanin-MRI as a sensitive technique to identify early changes in AD.

Glial reactivity and T cell infiltration in frontotemporal lobar degeneration with tau pathology.

Frontotemporal lobar degeneration with tau (FTLD-tau) is a group of tauopathies that underlie ∼50% of FTLD cases. Identification of genetic risk variants related to innate/adaptive immunity have highlighted a role for neuroinflammation and neuroimmune interactions in FTLD. Studies have shown microglial and astrocyte activation together with T cell infiltration in the brain of THY-Tau22 tauopathy mice. However, this remains to be confirmed in FTLD-tau patients. We conducted a detailed post-mortem study of FTLD-tau cases including 45 progressive supranuclear palsy with clinical frontotemporal dementia, 33 Pick's disease, 12 FTLD-MAPT and 52 control brains to characterize the link between phosphorylated tau (pTau) epitopes and the innate and adaptive immunity. Tau pathology was assessed in the cerebral cortex using antibodies directed against: Tau-2 (phosphorylated and unphosphorylated tau), AT8 (pSer202/pThr205), AT100 (pThr212/pSer214), CP13 (pSer202), PHF1 (pSer396/pSer404), pThr181 and pSer356. The immunophenotypes of microglia and astrocytes were assessed with phenotypic markers (Iba1, CD68, HLA-DR, CD64, CD32a, CD16 for microglia and GFAP, EAAT2, glutamine synthetase and ALDH1L1 for astrocytes). The adaptive immune response was explored via CD4+ and CD8+ T cell quantification and the neuroinflammatory environment was investigated via the expression of 30 inflammatory-related proteins using V-Plex Meso Scale Discovery. As expected, all pTau markers were increased in FTLD-tau cases compared to controls. pSer356 expression was greatest in FTLD-MAPT cases versus controls (P < 0.0001), whereas the expression of other markers was highest in Pick's disease. Progressive supranuclear palsy with frontotemporal dementia consistently had a lower pTau protein load compared to Pick's disease across tau epitopes. The only microglial marker increased in FTLD-tau was CD16 (P = 0.0292) and specifically in FTLD-MAPT cases (P = 0.0150). However, several associations were detected between pTau epitopes and microglia, supporting an interplay between them. GFAP expression was increased in FTLD-tau (P = 0.0345) with the highest expression in Pick's disease (P = 0.0019), while ALDH1L1 was unchanged. Markers of astrocyte glutamate cycling function were reduced in FTLD-tau (P = 0.0075; Pick's disease: P < 0.0400) implying astrocyte reactivity associated with a decreased glutamate cycling activity, which was further associated with pTau expression. Of the inflammatory proteins assessed in the brain, five chemokines were upregulated in Pick's disease cases (P < 0.0400), consistent with the recruitment of CD4+ (P = 0.0109) and CD8+ (P = 0.0014) T cells. Of note, the CD8+ T cell infiltration was associated with pTau epitopes and microglial and astrocytic markers. Our results highlight that FTLD-tau is associated with astrocyte reactivity, remarkably little activation of microglia, but involvement of adaptive immunity in the form of chemokine-driven recruitment of T lymphocytes.

The mitochondrial protein TSPO in Alzheimer's disease: relation to the severity of AD pathology and the neuroinflammatory environment.

The 18kD translocator protein (TSPO) is used as a positron emission tomography (PET) target to quantify neuroinflammation in patients. In Alzheimer's disease (AD), the cerebellum is the pseudo-reference region for comparison with the cerebral cortex due to the absence of AD pathology and lower levels of TSPO. However, using the cerebellum as a pseudo-reference region is debated, with other brain regions suggested as more suitable. This paper aimed to establish the neuroinflammatory differences between the temporal cortex and cerebellar cortex, including TSPO expression. Using 60 human post-mortem samples encompassing the spectrum of Braak stages (I-VI), immunostaining for pan-Aß, hyperphosphorylated (p)Tau, TSPO and microglial proteins Iba1, HLA-DR and MSR-A was performed in the temporal cortex and cerebellum. In the cerebellum, Aß but not pTau, increased over the course of the disease, in contrast to the temporal cortex, where both proteins were significantly increased. TSPO increased in the temporal cortex, more than twofold in the later stages of AD compared to the early stages, but not in the cerebellum. Conversely, Iba1 increased in the cerebellum, but not in the temporal cortex. TSPO was associated with pTau in the temporal cortex, suggesting that TSPO positive microglia may be reacting to pTau itself and/or neurodegeneration at later stages of AD. Furthermore, the neuroinflammatory microenvironment was examined, using MesoScale Discovery assays, and IL15 only was significantly increased in the temporal cortex. Together this data suggests that the cerebellum maintains a more homeostatic environment compared to the temporal cortex, with a consistent TSPO expression, supporting its use as a pseudo-reference region for quantification in TSPO PET scans.

Clinical impact of anti-inflammatory microglia and macrophage phenotypes at glioblastoma margins.

Glioblastoma is a devastating brain cancer for which effective treatments are required. Tumour-associated microglia and macrophages promote glioblastoma growth in an immune-suppressed microenvironment. Most recurrences occur at the invasive margin of the surrounding brain, yet the relationships between microglia/macrophage phenotypes, T cells and programmed death-ligand 1 (an immune checkpoint) across human glioblastoma regions are understudied. In this study, we performed a quantitative immunohistochemical analysis of 15 markers of microglia/macrophage phenotypes (including anti-inflammatory markers triggering receptor expressed on myeloid cells 2 and CD163, and the low-affinity-activating receptor CD32a), T cells, natural killer cells and programmed death-ligand 1, in 59 human IDH1-wild-type glioblastoma multi-regional samples (n = 177; 1 sample at tumour core, 2 samples at the margins: the infiltrating zone and leading edge). Assessment was made for the prognostic value of markers; the results were validated in an independent cohort. Microglia/macrophage motility and activation (Iba1, CD68), programmed death-ligand 1 and CD4+ T cells were reduced, and homeostatic microglia (P2RY12) were increased in the invasive margins compared with the tumour core. There were significant positive correlations between microglia/macrophage markers CD68 (phagocytic)/triggering receptor expressed on myeloid cells 2 (anti-inflammatory) and CD8+ T cells in the invasive margins but not in the tumour core (P < 0.01). Programmed death-ligand 1 expression was associated with microglia/macrophage markers (including anti-inflammatory) CD68, CD163, CD32a and triggering receptor expressed on myeloid cells 2, only in the leading edge of glioblastomas (P < 0.01). Similarly, there was a positive correlation between programmed death-ligand 1 expression and CD8+ T-cell infiltration in the leading edge (P < 0.001). There was no relationship between CD64 (a receptor for autoreactive T-cell responses) and CD8+/CD4+ T cells, or between the microglia/macrophage antigen presentation marker HLA-DR and microglial motility (Iba1) in the tumour margins. Natural killer cell infiltration (CD335+) correlated with CD8+ T cells and with CD68/CD163/triggering receptor expressed on myeloid cells 2 anti-inflammatory microglia/macrophages at the leading edge. In an independent large glioblastoma cohort with transcriptomic data, positive correlations between anti-inflammatory microglia/macrophage markers (triggering receptor expressed on myeloid cells 2, CD163 and CD32a) and CD4+/CD8+/programmed death-ligand 1 RNA expression were validated (P < 0.001). Finally, multivariate analysis showed that high triggering receptor expressed on myeloid cells 2, programmed death-ligand 1 and CD32a expression at the leading edge were significantly associated with poorer overall patient survival (hazard ratio = 2.05, 3.42 and 2.11, respectively), independent of clinical variables. In conclusion, anti-inflammatory microglia/macrophages, CD8+ T cells and programmed death-ligand 1 are correlated in the invasive margins of glioblastoma, consistent with immune-suppressive interactions. High triggering receptor expressed on myeloid cells 2, programmed death-ligand 1 and CD32a expression at the human glioblastoma leading edge are predictors of poorer overall survival. Given substantial interest in targeting microglia/macrophages, together with immune checkpoint inhibitors in cancer, these data have major clinical implications.

How honey bees make fast and accurate decisions.

Honey bee ecology demands they make both rapid and accurate assessments of which flowers are most likely to offer them nectar or pollen. To understand the mechanisms of honey bee decision-making, we examined their speed and accuracy of both flower acceptance and rejection decisions. We used a controlled flight arena that varied both the likelihood of a stimulus offering reward and punishment and the quality of evidence for stimuli. We found that the sophistication of honey bee decision-making rivalled that reported for primates. Their decisions were sensitive to both the quality and reliability of evidence. Acceptance responses had higher accuracy than rejection responses and were more sensitive to changes in available evidence and reward likelihood. Fast acceptances were more likely to be correct than slower acceptances; a phenomenon also seen in primates and indicative that the evidence threshold for a decision changes dynamically with sampling time. To investigate the minimally sufficient circuitry required for these decision-making capacities, we developed a novel model of decision-making. Our model can be mapped to known pathways in the insect brain and is neurobiologically plausible. Our model proposes a system for robust autonomous decision-making with potential application in robotics.

In the natural world, decision-making processes are often intricate and challenging. Animals frequently encounter situations where they have limited information on which to rely to guide them, yet even simple choices can have far-reaching impact on survival. Each time a bee sets out to collect nectar, for example, it must use tiny variations in colour or odour to decide which flower it should land on and explore. Each 'mistake' is costly, wasting energy and exposing the insect to potential dangers. To learn how to refine their choices through trial-and-error, bees only have at their disposal a brain the size of a sesame seed, which contains fewer than a million neurons. And yet, they excel at this task, being both quick and accurate. The underlying mechanisms which drive these remarkable decision-making capabilities remain unclear. In response, MaBouDi et al. aimed to explore which strategies honeybees adopt to forage so effectively, and the neural systems that may underlie them. To do so, they released the insects in a 'field' containing artificial flowers in five different colours. The bees were trained to link each colour with a certain likelihood of receiving either a sugary liquid (reward) or bitter quinine (punishment); they were then tested on this knowledge. Next, MaBouDi et al. recorded how the bees would navigate a 'reduced evidence' test, where the colour of the flowers were ambiguous and consisted in various blends of the originally rewarded or punished colours; and a 'reduced reward likelihood' test, where the sweet recompense was offered less often than before. Response times and accuracy rates revealed a complex pattern of decision-making processes. How quickly the insects made a choice, and the types of mistakes they made (such as deciding to explore a non-rewarded flower, or to ignore a rewarded one) were dependent on both the quality of the evidence and the certainty of the reward. Such sophistication and subtlety in decision-making is comparable to that of primates. Next, MaBouDi et al. developed a computational model which could faithfully replicate the pattern of decisions exhibited by the bees, while also being plausible biologically. This approach offered insights into how a small brain could execute such complex choices 'on the fly', and the type of neural circuits that would be required. Going forward, this knowledge could be harnessed to design more efficient decision-making algorithms for artificial systems, and in particular for autonomous robotics.

Amyloid-related imaging abnormalities (ARIA): radiological, biological and clinical characteristics.

Excess accumulation and aggregation of toxic soluble and insoluble amyloid-ß species in the brain are a major hallmark of Alzheimer's disease. Randomized clinical trials show reduced brain amyloid-ß deposits using monoclonal antibodies that target amyloid-ß and have identified MRI signal abnormalities called amyloid-related imaging abnormalities (ARIA) as possible spontaneous or treatment-related adverse events. This review provides a comprehensive state-of-the-art conceptual review of radiological features, clinical detection and classification challenges, pathophysiology, underlying biological mechanism(s) and risk factors/predictors associated with ARIA. We summarize the existing literature and current lines of evidence with ARIA-oedema/effusion (ARIA-E) and ARIA-haemosiderosis/microhaemorrhages (ARIA-H) seen across anti-amyloid clinical trials and therapeutic development. Both forms of ARIA may occur, often early, during anti-amyloid-ß monoclonal antibody treatment. Across randomized controlled trials, most ARIA cases were asymptomatic. Symptomatic ARIA-E cases often occurred at higher doses and resolved within 3-4 months or upon treatment cessation. Apolipoprotein E haplotype and treatment dosage are major risk factors for ARIA-E and ARIA-H. Presence of any microhaemorrhage on baseline MRI increases the risk of ARIA. ARIA shares many clinical, biological and pathophysiological features with Alzheimer's disease and cerebral amyloid angiopathy. There is a great need to conceptually link the evident synergistic interplay associated with such underlying conditions to allow clinicians and researchers to further understand, deliberate and investigate on the combined effects of these multiple pathophysiological processes. Moreover, this review article aims to better assist clinicians in detection (either observed via symptoms or visually on MRI), management based on appropriate use recommendations, and general preparedness and awareness when ARIA are observed as well as researchers in the fundamental understanding of the various antibodies in development and their associated risks of ARIA. To facilitate ARIA detection in clinical trials and clinical practice, we recommend the implementation of standardized MRI protocols and rigorous reporting standards. With the availability of approved amyloid-ß therapies in the clinic, standardized and rigorous clinical and radiological monitoring and management protocols are required to effectively detect, monitor, and manage ARIA in real-world clinical settings.

Rac2 regulates immune complex-mediated granule polarization and exocytosis in neutrophils.

A key molecule for neutrophil degranulation is Rac2 guanosine triphosphatase. Neutrophils from Rac2 knockout mice (Rac2-/-) exhibit impaired primary granule exocytosis in response to cytochalasin B/f-Met-Leu-Phe, while secondary and tertiary granule release is unaffected. Coronin 1A, a protein involved in actin remodeling, is diminished in Rac2-/- neutrophils. However, primary granule exocytosis from Rac2-/- neutrophils has not been determined using more immunologically relevant stimuli. We sought to determine the role of Rac2 in degranulation and actin cytoskeleton rearrangement in response to immobilized immune complexes and relate this to intracellular coronin 1A localization. We used bone marrow neutrophils from wild-type and Rac2-/- mice stimulated with immobilized immune complexes. Secretion of primary (myeloperoxidase), secondary (lactoferrin), and tertiary granule (MMP-2 and MMP-9) products was evaluated. Subcellular colocalization of coronin 1A with actin and the primary granule marker CD63 was determined by deconvolution microscopy. We found major differences in myeloperoxidase, MMP-2, and MMP-9 but not lactoferrin release, along with diminished filopodia formation, CD63 polarization, and colocalization of coronin 1A with CD63 in immune complex-stimulated Rac2-/- bone marrow neutrophils. Rac2 and coronin 1A were found associated with granules in cytochalasin B/f-Met-Leu-Phe-activated human neutrophils. This report confirms a role for Rac2 in immunologically relevant stimulation of neutrophil granule exocytosis. Rac2 appears to attach to neutrophil granules, polarize CD63+ granules to the cell surface in a manner dependent on coronin 1A, and induce filopodia formation. Our studies provide insight into mechanisms of Rac2-mediated regulation of granule exocytosis.

Asynchrony rescues statistically optimal group decisions from information cascades through emergent leaders.

It is usually assumed that information cascades are most likely to occur when an early but incorrect opinion spreads through the group. Here, we analyse models of confidence-sharing in groups and reveal the opposite result: simple but plausible models of naive-Bayesian decision-making exhibit information cascades when group decisions are synchronous; however, when group decisions are asynchronous, the early decisions reached by Bayesian decision-makers tend to be correct and dominate the group consensus dynamics. Thus early decisions actually rescue the group from making errors, rather than contribute to it. We explore the likely realism of our assumed decision-making rule with reference to the evolution of mechanisms for aggregating social information, and known psychological and neuroscientific mechanisms.

Localized microglia dysregulation impairs central nervous system myelination in development.

Myelination of neuronal axons is a critical aspect of central nervous system development and function. However, the fundamental cellular and molecular mechanisms influencing human developmental myelination and its failure are not fully understood. Here, we used digital spatial transcriptomics of a rare bank of human developing white matter to uncover that a localized dysregulated innate immune response is associated with impeded myelination. We identified that poorly myelinating areas have a distinct signature of Type II interferon signalling in microglia/macrophages, relative to adjacent myelinating areas. This is associated with a surprising increase in mature oligodendrocytes, which fail to form myelin processes appropriately. We functionally link these findings by showing that conditioned media from interferon-stimulated microglia is sufficient to dysregulate myelin process formation by oligodendrocytes in culture. We identify the Type II interferon inducer, Osteopontin (SPP1), as being upregulated in poorly myelinating brains, indicating a potential biomarker. Our results reveal the importance of microglia-mature oligodendrocyte interaction and interferon signaling in regulating myelination of the developing human brain.

Effect of macrocyclization and tetramethylrhodamine labeling on chemokine binding peptides.

Receptor-derived peptides have played an important role in elucidating chemokine-receptor interactions. For the inflammatory chemokine CXC-class chemokine ligand 8 (CXCL8), a site II-mimetic peptide has been derived from parts of extracellular loops 2 and 3 and adjacent transmembrane helices of its receptor CXC-class chemokine receptor 1 (Helmer et al., RSC Adv., 2015, 5, 25657). The peptide sequence with a C-terminal glutamine did not bind to CXCL8, whereas one with a C-terminal glutamate did but with low micromolar affinity. We sought to improve the affinity and protease stability of the latter peptide through cyclization while also cyclizing the former for control purposes. To identify a cyclization strategy that permits a receptor-like interaction, we conducted a molecular dynamics simulation of CXCL8 in complex with full-length CXC-class chemokine receptor 1. We introduced a linker to provide an appropriate spacing between the termini and used an on-resin side-chain-to-tail cyclization strategy. Upon chemokine binding, the fluorescence intensity of the tetramethylrhodamine (TAMRA)-labeled cyclic peptides increased whereas the fluorescence anisotropy decreased. Additional molecular dynamics simulations indicated that the fluorophore interacts with the peptide macrocycle so that chemokine binding leads to its displacement and observed changes in fluorescence. Macrocyclization of both 18-amino acid-long peptides led to the same low micromolar affinity for CXCL8. Likewise, both TAMRA-labeled linear peptides interacted with CXCL8 with similar affinities. Interestingly, the linear TAMRA-labeled peptides were more resistant to tryptic digestion than the unlabeled counterparts, whereas the cyclized peptides were not degraded at all. We conclude that the TAMRA fluorophore tends to interact with peptides altering their protease stability and behavior in fluorescence-based assays.

Magnitude-sensitive reaction times reveal non-linear time costs in multi-alternative decision-making.

Optimality analysis of value-based decisions in binary and multi-alternative choice settings predicts that reaction times should be sensitive only to differences in stimulus magnitudes, but not to overall absolute stimulus magnitude. Yet experimental work in the binary case has shown magnitude sensitive reaction times, and theory shows that this can be explained by switching from linear to multiplicative time costs, but also by nonlinear subjective utility. Thus disentangling explanations for observed magnitude sensitive reaction times is difficult. Here for the first time we extend the theoretical analysis of geometric time-discounting to ternary choices, and present novel experimental evidence for magnitude-sensitivity in such decisions, in both humans and slime moulds. We consider the optimal policies for all possible combinations of linear and geometric time costs, and linear and nonlinear utility; interestingly, geometric discounting emerges as the predominant explanation for magnitude sensitivity.

The spatiotemporal dynamics of microglia across the human lifespan.

Microglia, the brain's resident macrophages, shape neural development and are key neuroimmune hubs in the pathological signatures of neurodevelopmental disorders. Despite the importance of microglia, their development has not been carefully examined in the human brain, and most of our knowledge derives from rodents. We aimed to address this gap in knowledge by establishing an extensive collection of 97 post-mortem tissues in order to enable quantitative, sex-matched, detailed analysis of microglia across the human lifespan. We identify the dynamics of these cells in the human telencephalon, describing waves in microglial density across gestation, infancy, and childhood, controlled by a balance of proliferation and apoptosis, which track key neurodevelopmental milestones. These profound changes in microglia are also observed in bulk RNA-seq and single-cell RNA-seq datasets. This study provides a detailed insight into the spatiotemporal dynamics of microglia across the human lifespan and serves as a foundation for elucidating how microglia contribute to shaping neurodevelopment in humans.

Glioblastoma, IDH-wildtype: A New Association with IgM Paraproteinaemic Neuropathy?

It is well recognized that B-cell clonal disorders such as Waldenstrom's macroglobulinaemia may affect the central nervous system by direct infiltration of malignant B cells (Bing-Neel syndrome). However, there is no recognition in the current literature of a clear link between paraproteinaemia and primary brain tumours such as glioma. We present 3 cases of classical IgM paraproteinaemic neuropathy who developed glioblastoma in the course of their illness following treatment with chemoimmunotherapy (CIT). Due to the progressive symptomatic nature of their neuropathy, all 3 patients were treated with CIT. The patients presented with glioblastoma, IDH-wildtype at 9 months, 5 years, and 6 years following treatment completion. None of the patients had unequivocal evidence of known predisposing factors for glioblastoma. Both disorders are exceedingly rare and the chance of random association is less than one in a million. Potential common pathogenic mechanisms include the influence of paraproteins and circulating lymphoplasmacytic cells on blood-brain permeability and CNS immune micro-environment as well as raised circulating angiogenic cytokines such as vascular endothelial growth factor. In cases with anti-myelin-associated glycoprotein (MAG) antibodies, surface MAG on glial cells may act as a target releasing cells from growth inhibition. We suggest that all glioblastoma cases be screened at diagnosis for serum paraproteins and that such cases be reported to central registries to establish the frequency of the association more accurately.

Negative feedback may suppress variation to improve collective foraging performance.

Social insect colonies use negative as well as positive feedback signals to regulate foraging behaviour. In ants and bees individual foragers have been observed to use negative pheromones or mechano-auditory signals to indicate that forage sources are not ideal, for example being unrewarded, crowded, or dangerous. Here we propose an additional function for negative feedback signals during foraging, variance reduction. We show that while on average populations will converge to desired distributions over forage patches both with and without negative feedback signals, in small populations negative feedback reduces variation around the target distribution compared to the use of positive feedback alone. Our results are independent of the nature of the target distribution, providing it can be achieved by foragers collecting only local information. Since robustness is a key aim for biological systems, and deviation from target foraging distributions may be costly, we argue that this could be a further important and hitherto overlooked reason that negative feedback signals are used by foraging social insects.