Architectural dysplasia in surgical margins and the risk of local relapse in oral cancer.

BACKGROUND: A major challenge in the clinical management of oral cavity squamous cell carcinoma is local relapse. Even when surgical margins are tumor-free, local relapses occur frequently, and relapse prediction by histology remains suboptimal. In leukoplakia, an oral potentially malignant disorder, the presence of architectural dysplasia is a critical risk factor for malignant transformation. This study aimed to investigate whether the presence of architectural dysplasia in oral cavity squamous cell carcinoma surgical margins is a risk factor for local relapse. METHODS: Hematoxylin and eosin-stained slides of resection margins from a consecutive cohort of surgically treated patients diagnosed with stage I-IV oral cavity squamous cell carcinoma between 2008 and 2014 were assessed for the presence of architectural dysplasia (N = 311). Five-year local relapse-free survival rates of oral cavity squamous cell carcinoma with architectural dysplasia were compared to those of oral cavity squamous cell carcinoma without architectural dysplasia. RESULTS: In total, 92 of 311 (29.6%) of oral cavity squamous cell carcinoma displayed architectural dysplasia in the margins. The presence of architectural dysplasia was associated with higher patient age, female sex, less pack years, lower cT-stage, and a cohesive tumor growth pattern. In oral cavity squamous cell carcinomas with architectural dysplasia, postoperative (chemo)radiotherapy was less often indicated compared with oral cavity squamous cell carcinoma without architectural dysplasia (19.5% vs. 36.1%, p = 0.009). Five-year local relapse-free survival was significantly lower in oral cavity squamous cell carcinoma with architectural dysplasia than in oral cavity squamous cell carcinoma without architectural dysplasia (83.1% vs. 94.9%, p = 0.017). CONCLUSIONS: Oral cavity squamous cell carcinoma arising in the background of architectural dysplasia displays relatively favorable clinical and histopathological characteristics. Nonetheless, the presence of architectural dysplasia in oral cavity squamous cell carcinoma surgical margins is associated with a higher risk of local relapse, indicating its clinical relevance.

The role of differentiated dysplasia in the prediction of malignant transformation of oral leukoplakia.

OBJECTIVE: Oral leukoplakia is the most common oral potentially malignant disorder. Malignant transformation of oral leukoplakia occurs at an annual rate of 1%-7%. WHO-defined classic epithelial dysplasia is an important predictor of malignant transformation of oral leukoplakia, but we have previously shown in a proof of concept study that prediction improves by incorporation of an architectural pattern of dysplasia, also coined as differentiated dysplasia. We aimed to analyze this finding in a larger cohort of patients. METHOD: For this retrospective study 176 oral leukoplakia patients were included. Biopsies for all patients were assessed for the presence of dysplasia and analyzed for cytokeratin 13 and 17 expression. Moreover, the inter-observer agreement for the diagnosis of differentiated dysplasia was determined. RESULTS: In total, 33 of 176 patients developed oral squamous cell carcinoma during follow-up. Presence of classic epithelial dysplasia increased cancer risk two-fold (HR = 2.18, p = 0.026). Lesions without classic epithelial dysplasia could be further risk-stratified by the presence of differentiated dysplasia (HR = 7.36, p < 0.001). Combined classic epithelial and differentiated dysplasia imparted a seven-fold increased risk of malignant transformation (7.34, p = 0.001). Inter-observer agreement for the diagnosis of dysplasia, including differentiated dysplasia, was moderate (κ = 0.56, p < 0.001). DISCUSSION: This study emphasizes the importance of the recognition of the architectural pattern of differentiated dysplasia as a separate entity for risk prediction of malignant transformation of oral leukoplakia. Presence of any pattern of dysplasia results in accurate prediction of malignant transformation risk of oral leukoplakia.

The value of regular follow-up of oral leukoplakia for early detection of malignant transformation.

OBJECTIVES: Evaluate whether regular follow-up of oral leukoplakia (OL) resulted in early detection of malignant transformation (MT). METHOD: Two hundred and twenty-two consecutive patients with OL (147 females, 75 males); median follow-up period of 64 months (range: 12-300). Three groups were distinguished: group A (n = 92) follow-up at the hospital; group B (n = 84) follow-up by their dentist; group C (n = 46) lost to follow-up. RESULTS: OLs in group B compared to group A, were smaller in size (<2 cm; p < 0.001), showed more hyperkeratosis (p < 0.001) and less moderate/severe dysplasia (p < 0.001). MT occurred in 45 (20%) patients: 32 (35%) in group A, five (6%) in group B and eight (17%) in group C. There was no significant difference in clinical tumour size between group A (median: 15 mm, range: 1-40) and group B (median: 10 mm, range: 3-25; p = 0.496). Tumour size was smaller for patients in groups A and B (median: 10 mm, range 1-40) compared to group C (median: 33 mm, range: 3-100; p = 0.003). There was a positive correlation between tumour size and interval between the last visit in all patients (p = 0.022). CONCLUSION: Regular follow-up of OL resulted in early detection of MT. If properly selected, follow-up of OL performed by the dentist seems feasible.

Pentraxin-3 is upregulated in the central nervous system during MS and EAE, but does not modulate experimental neurological disease.

Pentraxin-3 (PTX3), an acute-phase protein released during inflammation, aids phagocytic clearance of pathogens and apoptotic cells, and plays diverse immunoregulatory roles in tissue injury. In neuroinflammatory diseases, like MS, resident microglia could become activated by endogenous agonists for Toll like receptors (TLRs). Previously we showed a strong TLR2-mediated induction of PTX3 in cultured human microglia and macrophages by HspB5, which accumulates in glia during MS. Given the anti-inflammatory effects of HspB5, we examined the contribution of PTX3 to these effects in MS and its animal model EAE. Our data indicate that TLR engagement effectively induces PTX3 expression in human microglia, and that such expression is readily detectable in MS lesions. Enhanced PTX3 expression is prominently expressed in microglia in preactive MS lesions, and in microglia/macrophages engaged in myelin phagocytosis in actively demyelinating lesions. Yet, we did not detect PTX3 in cerebrospinal fluid of MS patients. PTX3 expression is also elevated in spinal cords during chronic relapsing EAE in Biozzi ABH mice, but the EAE severity and time course in PTX3-deficient mice did not differ from WT mice. Moreover, systemic PTX3 administration did not alter the disease onset or severity. Our findings reveal local functions of PTX3 during neuroinflammation in facilitating myelin phagocytosis, but do not point to a role for PTX3 in controlling the development of autoimmune neuroinflammation.

Immunological memory to hyperphosphorylated tau in asymptomatic individuals.

Several reports have described the presence of antibodies against Alzheimer's disease-associated hyperphosphorylated forms of tau in serum of healthy individuals. To characterize the specificities that can be found, we interrogated peripheral IgG+ memory B cells from asymptomatic blood donors for reactivity to a panel of phosphorylated tau peptides using a single-cell screening assay. Antibody sequences were recovered, cloned, and expressed as full-length IgGs. In total, 52 somatically mutated tau-binding antibodies were identified, corresponding to 35 unique clonal families. Forty-one of these antibodies recognize epitopes in the proline-rich and C-terminal domains, and binding of 26 of these antibodies is strictly phosphorylation dependent. Thirteen antibodies showed inhibitory activity in a P301S lysate seeded in vitro tau aggregation assay. Two such antibodies, CBTAU-7.1 and CBTAU-22.1, which bind to the proline-rich and C-terminal regions of tau, respectively, were characterized in more detail. CBTAU-7.1 recognizes an epitope that is similar to that of murine anti-PHF antibody AT8, but has different phospho requirements. Both CBTAU-7.1 and CBTAU-22.1 detect pathological tau deposits in post-mortem brain tissue. CBTAU-7.1 reveals a similar IHC distribution pattern as AT8, immunostaining (pre)tangles, threads, and neuritic plaques. CBTAU-22.1 shows selective detection of neurofibrillary changes by IHC. Taken together, these results suggest the presence of an ongoing antigen-driven immune response against tau in healthy individuals. The wide range of specificities to tau suggests that the human immune repertoire may contain antibodies that can serve as biomarkers or be exploited for therapy.

Ageing and recurrent episodes of neuroinflammation promote progressive experimental autoimmune encephalomyelitis in Biozzi ABH mice.

Current therapies for multiple sclerosis (MS) reduce the frequency of relapses by modulating adaptive immune responses but fail to limit the irreversible neurodegeneration driving progressive disability. Experimental autoimmune encephalomyelitis (EAE) in Biozzi ABH mice recapitulates clinical features of MS including relapsing-remitting episodes and secondary-progressive disability. To address the contribution of recurrent inflammatory events and ageing as factors that amplify progressive neurological disease, we examined EAE in 8- to 12-week-old and 12-month-old ABH mice. Compared with the relapsing-remitting (RREAE) and secondary progressive (SPEAE) EAE observed in young mice, old mice developed progressive disease from onset (PEAE) associated with pronounced axonal damage and increased numbers of CD3(+) T cells and microglia/macrophages, but not B cells. Whereas the clinical neurological features of PEAE and SPEAE were comparable, the pathology was distinct. SPEAE was associated with significantly reduced perivascular infiltrates and T-cell numbers in the central nervous system (CNS) compared with PEAE and the acute phase of RREAE. In contrast to perivascular infiltrates that declined during progression from RREAE into SPEAE, the numbers of microglia clusters remained constant. Similar to what is observed during MS, the microglia clusters emerging during EAE were associated with axonal damage and oligodendrocytes expressing heat-shock protein B5, but not lymphocytes. Taken together, our data reveal that the course of EAE is dependent on the age of the mice. Younger mice show a relapsing-remitting phase followed by progressive disease, whereas old mice immediately show progression. This indicates that recurrent episodes of inflammation in the CNS, as well as age, contribute to progressive neurological disease.

GM-CSF promotes migration of human monocytes across the blood brain barrier.

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Infiltration of monocytes into the CNS is crucial for disease onset and progression. Animal studies indicate that granulocyte-macrophages colony-stimulating factor (GM-CSF) may play an essential role in this process, possibly by acting on the migratory capacities of myeloid cells across the blood-brain barrier. This study describes the effect of GM-CSF on human monocytes, macrophages, and microglia. Furthermore, the expression of GM-CSF and its receptor was investigated in the CNS under healthy and pathological conditions. We show that GM-CSF enhances monocyte migration across human blood-brain barrier endothelial cells in vitro. Next, immunohistochemical analysis on human brain tissues revealed that GM-CSF is highly expressed by microglia and macrophages in MS lesions. The GM-CSF receptor is expressed by neurons in the rim of combined gray/white matter lesions and astrocytes. Finally, the effect of GM-CSF on human macrophages was determined, revealing an intermediate activation status, with a phenotype similar to that observed in active MS lesions. Together our data indicate that GM-CSF is a powerful stimulator of monocyte migration, and is abundantly present in the inflamed CNS where it may act as an activator of macrophages and microglia.

Expression of IL-1ß in rhesus EAE and MS lesions is mainly induced in the CNS itself.

BACKGROUND: Interleukin (IL)-1ß is a pro-inflammatory cytokine that plays a role in the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), the animal model for MS. Yet, detailed studies on IL-1ß expression in different stages of MS lesion development and a comparison of IL-1ß expression in MS and EAE are lacking. METHODS: Here, we performed an extensive characterization of IL-1ß expression in brain tissue of MS patients, which included different MS lesion types, and in brain tissue of rhesus macaques with EAE. RESULTS: In rhesus EAE brain tissue, we observed prominent IL-1ß staining in MHC class II(+) cells within perivascular infiltrates and at the edges of large demyelinating lesions. Surprisingly, staining was localized to resident microglia or differentiated macrophages rather than to infiltrating monocytes, suggesting that IL-1ß expression is induced within the central nervous system (CNS). By contrast, IL-1ß staining in MS brain tissue was much less pronounced. Staining was found in the parenchyma of active and chronic active MS lesions and in nodules of MHC class II(+) microglia in otherwise normal appearing white matter. IL-1ß expression was detected in a minority of the nodules only, which could not be distinguished by the expression of pro- and anti-inflammatory markers. These nodules were exclusively found in MS, and it remains to be determined whether IL-1ß(+) nodules are destined to progress into active lesions or whether they merely reflect a transient response to cellular stress. CONCLUSIONS: Although the exact localization and relative intensity of IL-1ß expression in EAE and MS is different, the staining pattern in both neuroinflammatory disorders is most consistent with the idea that the expression of IL-1ß during lesion development is induced in the tissue rather than in the periphery.

Oligodendrocyte-microglia cross-talk in the central nervous system.

Communication between the immune system and the central nervous system (CNS) is exemplified by cross-talk between glia and neurons shown to be essential for maintaining homeostasis. While microglia are actively modulated by neurons in the healthy brain, little is known about the cross-talk between oligodendrocytes and microglia. Oligodendrocytes, the myelin-forming cells in the CNS, are essential for the propagation of action potentials along axons, and additionally serve to support neurons by producing neurotrophic factors. In demyelinating diseases such as multiple sclerosis, oligodendrocytes are thought to be the victims. Here, we review evidence that oligodendrocytes also have strong immune functions, express a wide variety of innate immune receptors, and produce and respond to chemokines and cytokines that modulate immune responses in the CNS. We also review evidence that during stress events in the brain, oligodendrocytes can trigger a cascade of protective and regenerative responses, in addition to responses that elicit progressive neurodegeneration. Knowledge of the cross-talk between microglia and oligodendrocytes may continue to uncover novel pathways of immune regulation in the brain that could be further exploited to control neuroinflammation and degeneration.

Inflammation in neurodegenerative diseases--an update.

Neurodegeneration, the progressive dysfunction and loss of neurons in the central nervous system (CNS), is the major cause of cognitive and motor dysfunction. While neuronal degeneration is well-known in Alzheimer's and Parkinson's diseases, it is also observed in neurotrophic infections, traumatic brain and spinal cord injury, stroke, neoplastic disorders, prion diseases, multiple sclerosis and amyotrophic lateral sclerosis, as well as neuropsychiatric disorders and genetic disorders. A common link between these diseases is chronic activation of innate immune responses including those mediated by microglia, the resident CNS macrophages. Such activation can trigger neurotoxic pathways leading to progressive degeneration. Yet, microglia are also crucial for controlling inflammatory processes, and repair and regeneration. The adaptive immune response is implicated in neurodegenerative diseases contributing to tissue damage, but also plays important roles in resolving inflammation and mediating neuroprotection and repair. The growing awareness that the immune system is inextricably involved in mediating damage as well as regeneration and repair in neurodegenerative disorders, has prompted novel approaches to modulate the immune system, although it remains whether these approaches can be used in humans. Additional factors in humans include ageing and exposure to environmental factors such as systemic infections that provide additional clues that may be human specific and therefore difficult to translate from animal models. Nevertheless, a better understanding of how immune responses are involved in neuronal damage and regeneration, as reviewed here, will be essential to develop effective therapies to improve quality of life, and mitigate the personal, economic and social impact of these diseases.

Demyelination during multiple sclerosis is associated with combined activation of microglia/macrophages by IFN-γ and alpha B-crystallin.

Activated microglia and macrophages play a key role in driving demyelination during multiple sclerosis (MS), but the factors responsible for their activation remain poorly understood. Here, we present evidence for a dual-trigger role of IFN-γ and alpha B-crystallin (HSPB5) in this context. In MS-affected brain tissue, accumulation of the molecular chaperone HSPB5 by stressed oligodendrocytes is a frequent event. We have shown before that this triggers a TLR2-mediated protective response in surrounding microglia, the molecular signature of which is widespread in normal-appearing brain tissue during MS. Here, we show that IFN-γ, which can be released by infiltrated T cells, changes the protective response of microglia and macrophages to HSPB5 into a robust pro-inflammatory classical response. Exposure of cultured microglia and macrophages to IFN-γ abrogated subsequent IL-10 induction by HSPB5, and strongly promoted HSPB5-triggered release of TNF-α, IL-6, IL-12, IL-1ß and reactive oxygen and nitrogen species. In addition, high levels of CXCL9, CXCL10, CXL11, several guanylate-binding proteins and the ubiquitin-like protein FAT10 were induced by combined activation with IFN-γ and HSPB5. As immunohistochemical markers for microglia and macrophages exposed to both IFN-γ and HSPB5, these latter factors were found to be selectively expressed in inflammatory infiltrates in areas of demyelination during MS. In contrast, they were absent from activated microglia in normal-appearing brain tissue. Together, our data suggest that inflammatory demyelination during MS is selectively associated with IFN-γ-induced re-programming of an otherwise protective response of microglia and macrophages to the endogenous TLR2 agonist HSPB5.

Design and evaluation of an immunology and pathology course that is tailored to today's dentistry students.

Curricular reform provides new opportunities to renovate important pillars of the dentistry curriculum, such as immunology and pathology, with novel approaches that appeal to new generations of students. When redesigning a course that integrates both immunology and pathology at the level that provides dentistry students with sustainable knowledge that is useful for their entire career, several challenges must be met. The objective of the present study was to describe the considerations involved in the design phase of such a new course. First, the course should be compatible with the new view on the incorporation of more active learning and teaching methods. Practically, this means that the course design should contain fewer lectures and more seminars and tutorials, where the students have fewer contact hours and actively engage in using recently acquired knowledge within a contextual background. A mandatory session of team-based learning provides opportunities to apply knowledge in combination with academic reasoning skills, teamwork, and communication. Second, for a 4-week course, choices must be made: students will not become immunologists nor pathologists in such a short period. A governing principle for this course's design is that it should be based on understanding the basic principles of immunology and pathology. The ultimate goal for the students is to make the course immuno-logical and patho-logical, challenging them to reach a next level but clearly without oversimplification. Part of the course design should allow room for students to further study an immunological topic of their own choice, thereby contributing to their immunological curiosity and to their academic development. Third, to make it tailored to a new generation of dentists, examples from the field of dentistry are actively integrated in all aspects of the course. Finally, the era of ChatGPT provides novel opportunities to use generative artificial intelligence (AI) tools in the learning process, but it demands critical thinking of how to use it in a newly designed course. A mid-course evaluation revealed that students acknowledged that immunology and pathology were presented as an integrated course. The final course evaluation endorsed the use of these various educational methods. These methods proved to be appropriate and logical choices for reaching the learning goals of the course.

Immune cell topography of head and neck cancer.

BACKGROUND: Approximately 50% of head and neck squamous cell carcinomas (HNSCC) recur after treatment with curative intent. Immune checkpoint inhibitors are treatment options for recurrent/metastatic HNSCC; however, less than 20% of patients respond. To increase this response rate, it is fundamental to increase our understanding of the spatial tumor immune microenvironment (TIME). METHODS: In total, 53 HNSCC specimens were included. Using a seven-color multiplex immunohistochemistry panel we identified tumor cells, CD163+macrophages, B cells, CD8+T cells, CD4+T helper cells and regulatory T cells (Tregs) in treatment-naive surgical resection specimens (n=29) and biopsies (n=18). To further characterize tumor-infiltrating CD8+T cells, we stained surgical resection specimens (n=12) with a five-color tumor-resident panel including CD103, Ki67, CD8 and pan-cytokeratin. Secretome analysis was performed on matched tumor suspensions (n=11) to measure protein levels. RESULTS: Based on CD8+T cell infiltrates, we identified four different immunotypes: fully infiltrated, stroma-restricted, immune-excluded, and immune-desert. We found higher cytokine levels in fully infiltrated tumors compared with other immunotypes. While the highest immune infiltrates were observed in the invasive margin for all immune cells, CD163+macrophages and Tregs had the highest tendency to infiltrate the tumor center. Within the tumor center, especially B cells stayed at the tumor stroma, whereas CD163+macrophages, followed by T cells, were more often localized within tumor fields. Also, B cells were found further away from other cells and often formed aggregates while T cells and CD163+macrophages tended to be more closely located to each other. Across resection specimens from various anatomical sites within the head and neck, oral cavity tumors exhibited the highest densities of Tregs. Moreover, the distance from B cells and T cells to tumor cells was shortest in oral cavity squamous cell carcinoma (OCSCC), suggesting more interaction between lymphocytes and tumor cells. Also, the fraction of T cells within 10 µm of CD163+macrophages was lowest in OCSCC, indicating fewer myeloid/T-cell suppressive interactions in OCSCC. CONCLUSIONS: We comprehensively described the TIME of HNSCC using a unique data set of resection specimens. We discovered that the composition, as well as the relative localization of immune cells in the TIME, differed in distinct anatomical sites of the head and neck.

Genomic Engineering of Oral Keratinocytes to Establish In Vitro Oral Potentially Malignant Disease Models as a Platform for Treatment Investigation.

Precancerous cells in the oral cavity may appear as oral potentially malignant disorders, but they may also present as dysplasia without visual manifestation in tumor-adjacent tissue. As it is currently not possible to prevent the malignant transformation of these oral precancers, new treatments are urgently awaited. Here, we generated precancer culture models using a previously established method for the generation of oral keratinocyte cultures and incorporated CRISPR/Cas9 editing. The generated cell lines were used to investigate the efficacy of a set of small molecule inhibitors. Tumor-adjacent mucosa and oral leukoplakia biopsies were cultured and genetically characterized. Mutations were introduced in CDKN2A and TP53 using CRISPR/Cas9 and combined with the ectopic activation of telomerase to generate cell lines with prolonged proliferation. The method was tested in normal oral keratinocytes and tumor-adjacent biopsies and subsequently applied to a large set of oral leukoplakia biopsies. Finally, a subset of the immortalized cell lines was used to assess the efficacy of a set of small molecule inhibitors. Culturing and genomic engineering was highly efficient for normal and tumor-adjacent oral keratinocytes, but success rates in oral leukoplakia were remarkably low. Knock-out of CDKN2A in combination with either the activation of telomerase or knock-out of TP53 seemed a prerequisite for immortalization. Prolonged culturing was accompanied by additional genetic aberrations in these cultures. The generated cell lines were more sensitive than normal keratinocytes to small molecule inhibitors of previously identified targets. In conclusion, while very effective for normal keratinocytes and tumor-adjacent biopsies, the success rate of oral leukoplakia cell culturing methods was very low. Genomic engineering enabled the prolonged culturing of OL-derived keratinocytes but was associated with acquired genetic changes. Further studies are required to assess to what extent the immortalized cultures faithfully represent characteristics of the cells in vivo.

Circulating T cell status and molecular imaging may predict clinical benefit of neoadjuvant PD-1 blockade in oral cancer.

BACKGROUND: Addition of neoadjuvant immune checkpoint inhibition to standard-of-care interventions for locally advanced oral cancer could improve clinical outcome. METHODS: In this study, 16 evaluable patients with stage III/IV oral cancer were treated with one dose of 480 mg nivolumab 3 weeks prior to surgery. Primary objectives were safety, feasibility, and suitability of programmed death receptor ligand-1 positron emission tomography (PD-L1 PET) as a biomarker for response. Imaging included 18F-BMS-986192 (PD-L1) PET and 18F-fluorodeoxyglucose (FDG) PET before and after nivolumab treatment. Secondary objectives included clinical and pathological response, and immune profiling of peripheral blood mononuclear cells (PBMCs) for response prediction. Baseline tumor biopsies and postnivolumab resection specimens were evaluated by histopathology. RESULTS: Grade III or higher adverse events were not observed and treatment was not delayed in relation to nivolumab administration and other study procedures. Six patients (38%) had a pathological response, of whom three (19%) had a major (≥90%) pathological response (MPR). Tumor PD-L1 PET uptake (quantified using standard uptake value) was not statistically different in patients with or without MPR (median 5.3 vs 3.4). All major responders showed a significantly postnivolumab decreased signal on FDG PET. PBMC immune phenotyping showed higher levels of CD8+ T cell activation in MPR patients, evidenced by higher baseline expression levels of PD-1, TIGIT, IFNγ and lower levels of PD-L1. CONCLUSION: Together these data support that neoadjuvant treatment of advanced-stage oral cancers with nivolumab was safe and induced an MPR in a promising 19% of patients. Response was associated with decreased FDG PET uptake as well as activation status of peripheral T cell populations.

Clusters of activated microglia in normal-appearing white matter show signs of innate immune activation.

BACKGROUND: In brain tissues from multiple sclerosis (MS) patients, clusters of activated HLA-DR-expressing microglia, also referred to as preactive lesions, are located throughout the normal-appearing white matter. The aim of this study was to gain more insight into the frequency, distribution and cellular architecture of preactive lesions using a large cohort of well-characterized MS brain samples. METHODS: Here, we document the frequency of preactive lesions and their association with distinct white matter lesions in a cohort of 21 MS patients. Immunohistochemistry was used to gain further insight into the cellular and molecular composition of preactive lesions. RESULTS: Preactive lesions were observed in a majority of MS patients (67%) irrespective of disease duration, gender or subtype of disease. Microglial clusters were predominantly observed in the vicinity of active demyelinating lesions and are not associated with T cell infiltrates, axonal alterations, activated astrocytes or blood-brain barrier disruption. Microglia in preactive lesions consistently express interleukin-10 and TNF-α, but not interleukin-4, whereas matrix metalloproteases-2 and -9 are virtually absent in microglial nodules. Interestingly, key subunits of the free-radical-generating enzyme NADPH oxidase-2 were abundantly expressed in microglial clusters. CONCLUSIONS: The high frequency of preactive lesions suggests that it is unlikely that most of them will progress into full-blown demyelinating lesions. Preactive lesions are not associated with blood-brain barrier disruption, suggesting that an intrinsic trigger of innate immune activation, rather than extrinsic factors crossing a damaged blood-brain barrier, induces the formation of clusters of activated microglia.

Astrocyte and Oligodendrocyte Cross-Talk in the Central Nervous System.

Over the last decade knowledge of the role of astrocytes in central nervous system (CNS) neuroinflammatory diseases has changed dramatically. Rather than playing a merely passive role in response to damage it is clear that astrocytes actively maintain CNS homeostasis by influencing pH, ion and water balance, the plasticity of neurotransmitters and synapses, cerebral blood flow, and are important immune cells. During disease astrocytes become reactive and hypertrophic, a response that was long considered to be pathogenic. However, recent studies reveal that astrocytes also have a strong tissue regenerative role. Whilst most astrocyte research focuses on modulating neuronal function and synaptic transmission little is known about the cross-talk between astrocytes and oligodendrocytes, the myelinating cells of the CNS. This communication occurs via direct cell-cell contact as well as via secreted cytokines, chemokines, exosomes, and signalling molecules. Additionally, this cross-talk is important for glial development, triggering disease onset and progression, as well as stimulating regeneration and repair. Its critical role in homeostasis is most evident when this communication fails. Here, we review emerging evidence of astrocyte-oligodendrocyte communication in health and disease. Understanding the pathways involved in this cross-talk will reveal important insights into the pathogenesis and treatment of CNS diseases.

Acute syphilitic meningitis in an HIV-infected patient.

We present a case of acute syphilitic meningitis in a 28-year old HIV-infected patient, presenting with a seizure. MRI revealed a meningeal lesion with cortical involvement, and the patient described previous treatment for syphilis. Final diagnosis was established by PCR and spirochete staining on a brain biopsy, upon which the patient was successfully treated with benzylpenicillin.

Pro-inflammatory activation of primary microglia and macrophages increases 18 kDa translocator protein expression in rodents but not humans.

The 18kDa Translocator Protein (TSPO) is the most commonly used tissue-specific marker of inflammation in positron emission tomography (PET) studies. It is expressed in myeloid cells such as microglia and macrophages, and in rodent myeloid cells expression increases with cellular activation. We assessed the effect of myeloid cell activation on TSPO gene expression in both primary human and rodent microglia and macrophages in vitro, and also measured TSPO radioligand binding with 3H-PBR28 in primary human macrophages. As observed previously, we found that TSPO expression increases (∼9-fold) in rodent-derived macrophages and microglia upon pro-inflammatory stimulation. However, TSPO expression does not increase with classical pro-inflammatory activation in primary human microglia (fold change 0.85 [95% CI 0.58-1.12], p = 0.47). In contrast, pro-inflammatory activation of human monocyte-derived macrophages is associated with a reduction of both TSPO gene expression (fold change 0.60 [95% CI 0.45-0.74], p = 0.02) and TSPO binding site abundance (fold change 0.61 [95% CI 0.49-0.73], p < 0.0001). These findings have important implications for understanding the biology of TSPO in activated macrophages and microglia in humans. They are also clinically relevant for the interpretation of PET studies using TSPO targeting radioligands, as they suggest changes in TSPO expression may reflect microglial and macrophage density rather than activation phenotype.