Direct Microbicidal Activity of Cytotoxic T-Lymphocytes

Cytotoxic T-lymphocytes (CTL) are famous for their ability to kill tumor, allogeneic and virus-infected cells. However, an emerging literature has now demonstrated that CTL also possess the ability to directly recognize and kill bacteria, parasites, and fungi. Here, we review past and recent findings demonstrating the direct microbicidal activity of both CD4+ and CD8+ CTL against various microbial pathogens. Further, this review will outline what is known regarding the mechanisms of direct killing and their underlying signalling pathways

Insula volumes in psychosis probands

Insula is postulated to be a critical cortical region with extensive cortico-limbic connections and is hypothesized to play a role in pain/auditory/facial affect processing and interoception. Morphological abnormalities in this region may contribute to schizophrenia (SZ), schizoaffective disorder (SAD), and psychotic Bipolar disorder (BDP) symptomatology. Previous studies of insula have led to somewhat inconsistent results. Few studies have separately examined the left and right insula's anterior and posterior components, which have distinct functional roles. This study will examine the morphological and cognitive changes which occur in psychosis within the left and right insula, bilateral insula, and anterior and posterior insula. Although the exact localization of these deficits is inconsistent, we postulate that control groups will have greater volume, thickness, and local Gyrification Index (LGI) across all measures compared to psychosis groups, with greater reductions confined to the anterior insula since it is hypothesized to play a role in higher-order processing. Due to the hypothesized decrease in LGI in psychosis groups, we postulate to see the most significant correlations in LGI, supporting the view that decreases in gyrification correlate to decreases in cognitive abilities (Gautam et al., 2015; Park et al., 2021). T1-MPRAGE scans were obtained using 3T MRI scans. Insula measurements were extracted using FreeSurfer (FS) 7.1 in healthy controls (NC=935) and psychosis probands (SZ=481, SAD=383, BDP=381). FS measures were correlated with cognition (verbal memory (VM), verbal fluency (VF), digit sequencing (DS), and symbol coding (SC)), and symptomatology in SZ/SAD/BPD. P values < 0.05 adjusted for False Discovery Rate (FDR) were reported. Our observations suggest structural alterations in the insula, predominantly in volume, thickness, and LGI, across affective and non-affective psychotic disorders. Though we observed relations between the insula and cognitive measures, we did not see correlations with symptomatology. Future studies will examine further the relation between insular structure and socio-emotional and self-processing believed to be related to the anterior insula

MIR137 polygenic risk for schizophrenia and ephrin-regulated pathway:Role in lateral ventricles and corpus callosum volume

Background/Objective:Enlarged lateral ventricle (LV) volume and decreased volume in the corpus callosum (CC) are hallmarks of schizophrenia (SZ). We previously showed an inverse correlation between LV and CC volumes in SZ, with global functioning decreasing with increased LV volume. This study investigates the relationship between LV volume, CC abnormalities, and the microRNA MIR137 and its regulated genes in SZ, because of MIR137’s essential role in neurodevelopment. Methods:Participants were 1224 SZ probands and 1466 unaffected controls from the GENUS Consortium. Brain MRI scans, genotype, and clinical data were harmonized across cohorts and employed in the analyses. Results:Increased LV volumes and decreased CC central, mid-anterior, and mid-posterior volumes were observed in SZ probands. The MIR137-regulated ephrin pathway was significantly associated with CC:LV ratio, explaining a significant proportion (3.42 %) of CC:LV variance, and more than for LV and CC separately. Other pathways explained variance in either CC or LV, but not both. CC:LV ratio was also positively correlated with Global Assessment of Functioning, supporting previous subsample findings. SNP-based heritability estimates were higher for CC central:LV ratio (0.79) compared to CC or LV separately.Discussion:Our results indicate that the CC:LV ratio is highly heritable, influenced in part by variation in the MIR137-regulated ephrin pathway. Findings suggest that the CC:LV ratio may be a risk indicator in SZ that correlates with global functioning.</p

MIR137 polygenic risk for schizophrenia and ephrin-regulated pathway:Role in lateral ventricles and corpus callosum volume

Background/Objective:Enlarged lateral ventricle (LV) volume and decreased volume in the corpus callosum (CC) are hallmarks of schizophrenia (SZ). We previously showed an inverse correlation between LV and CC volumes in SZ, with global functioning decreasing with increased LV volume. This study investigates the relationship between LV volume, CC abnormalities, and the microRNA MIR137 and its regulated genes in SZ, because of MIR137’s essential role in neurodevelopment. Methods:Participants were 1224 SZ probands and 1466 unaffected controls from the GENUS Consortium. Brain MRI scans, genotype, and clinical data were harmonized across cohorts and employed in the analyses. Results:Increased LV volumes and decreased CC central, mid-anterior, and mid-posterior volumes were observed in SZ probands. The MIR137-regulated ephrin pathway was significantly associated with CC:LV ratio, explaining a significant proportion (3.42 %) of CC:LV variance, and more than for LV and CC separately. Other pathways explained variance in either CC or LV, but not both. CC:LV ratio was also positively correlated with Global Assessment of Functioning, supporting previous subsample findings. SNP-based heritability estimates were higher for CC central:LV ratio (0.79) compared to CC or LV separately.Discussion:Our results indicate that the CC:LV ratio is highly heritable, influenced in part by variation in the MIR137-regulated ephrin pathway. Findings suggest that the CC:LV ratio may be a risk indicator in SZ that correlates with global functioning.</p

Src family kinases are required for nk cell microbicidal activity to cryptococcus neoformans

Bibliography: p. 106-125A page is in colour.NK cells are well known for their ability to recognize and kill tumor and virally infected cells. Numerous studies have now demonstrated that NK cells also possess the ability to directly recognize and kill bacteria, parasites and fungi such as the pathogenic fungus Cryptococcus neoformans. However, the precise signalling pathways governing NK cell microbicidal activity are still unknown. Previously, it was reported that activation of a conserved PI3K -ERK l /2 pathway is necessary for NK cell anticryptococcal activity. Using YT (NK-like cell line) and primary human NK cells, we sought to identify the upstream signalling elements that lead to the activation of this pathway. We demonstrate that Src family kinases, in particular Fyn, were activated in response to C. neoformans. Furthermore, pharmacologic inhibition with a Src family kinase inhibitor (dasatinib) was found to block C. neoformans induced activation of PI3K and ERKI/2 and abrogate cryptococcal killing. At the same time, dasatinib was observed to disrupt the polarization of perforin-containing granules towards the NK cell-cryptococcal synapse but had no effect on conjugate fom1ation between NK cells and C. neoformans. Finally, double (but not single) siRNA knockdown of two specific Src family kinases, Fyn and Lyn, was found to completely block cryptococcal killing. \Ve also demonstrate that neither Syk nor ZAP-70 were activated in response to C. neoformans. Moreover, anticryptococcal activity was found to be insensitive to both pham1acologic inhibition with a Syk inhibitor (Syk inhibitor II) and siRNA knockdown of ZAP-70. Together these data demonstrate a mechanism whereby the Src family kinases, Fyn and Lyn, redundantly mediate anticryptococcal activity through the IT AM (Syk/ZAP-70) independent activation of PBK-ERKI/2, which in turn facilitates killing by inducing the polarization of perforin-containing granules to the NK cell-cryptococcal synapse

Direct Microbicidal Activity of Cytotoxic T-Lymphocytes

Cytotoxic T-lymphocytes (CTL) are famous for their ability to kill tumor, allogeneic and virus-infected cells. However, an emerging literature has now demonstrated that CTL also possess the ability to directly recognize and kill bacteria, parasites, and fungi. Here, we review past and recent findings demonstrating the direct microbicidal activity of both CD4+ and CD8+ CTL against various microbial pathogens. Further, this review will outline what is known regarding the mechanisms of direct killing and their underlying signalling pathways.Peer Reviewe

An acidic microenvironment increases NK cell killing of Cryptococcus neoformans and Cryptococcus gattii by enhancing perforin degranulation.

Cryptococcus gattii and Cryptococcus neoformans are encapsulated yeasts that can produce a solid tumor-like mass or cryptococcoma. Analogous to malignant tumors, the microenvironment deep within a cryptococcoma is acidic, which presents unique challenges to host defense. Analogous to malignant cells, NK cells kill Cryptococcus. Thus, as in tumor defense, NK cells must kill yeast cells across a gradient from physiologic pH to less than 6 in the center of the cryptococcoma. As acidic pH inhibits anti-tumor activities of NK cells, we sought to determine if there was a similar reduction in the anticryptococcal activity of NK cells. Surprisingly, we found that both primary human NK cells and the human NK cell line, YT, have preserved or even enhanced killing of Cryptococcus in acidic, compared to physiological, pH. Studies to explore the mechanism of enhanced killing revealed that acidic pH does not increase the effector to target ratio, binding of cytolytic cells to Cryptococcus, or the active perforin content in effector cells. By contrast, perforin degranulation was greater at acidic pH, and increased degranulation was preceded by enhanced ERK1/2 phosphorylation, which is essential for killing. Moreover, using a replication defective ras1 knockout strain of Cryptococcus increased degranulation occurred during more rapid replication of the organisms. Finally, NK cells were found intimately associated with C. gattii within the cryptococcoma of a fatal infection. These results suggest that NK cells have amplified signaling, degranulation, and greater killing at low pH and when the organisms are replicating quickly, which would help maintain microbicidal host defense despite an acidic microenvironment

Cryptococcomas contain numerous granzyme B positive, but very few perforin positive NK cells.

<p>Case 1: The brain was removed at autopsy and fixed in formalin with subsequent sectioning and examination. Sections were taken from the cryptococcoma in the cerebral cortex and stained with mucicarmine (200×) (A); or stained with PAS and labeled with either anti-CD56 (400×) (B); anti-CD57 (600×) (C); anti-granzyme B (1000×) (D); or anti-perforin (E, 600×) antibody. <i>Cryptococcus</i> (open arrow) in association with labeled cells (solid arrows) are shown. Perforin positive cells (brown) in NK cell lymphoma in lung, shown as a positive control for perforin (F). Case 2: Wedge resection of lung cryptococcoma, fixed in formalin with subsequent sectioning, PAS staining and labeled with either anti-CD57 (G, 400×), anti-granzyme B (H, 1000×) or anti-perforin (I, 600×). No organisms are present in figure G. The organisms stain bright pink with PAS, whilst positive staining for antigens is dark brown.</p