Mitochondrial fusion and altered beta-oxidation drive muscle wasting in a Drosophila cachexia model

Cancer cachexia is a tumour-induced wasting syndrome, characterised by extreme loss of skeletal muscle. Defective mitochondria can contribute to muscle wasting; however, the underlying mechanisms remain unclear. Using a Drosophila larval model of cancer cachexia, we observed enlarged and dysfunctional muscle mitochondria. Morphological changes were accompanied by upregulation of beta-oxidation proteins and depletion of muscle glycogen and lipid stores. Muscle lipid stores were also decreased in Colon-26 adenocarcinoma mouse muscle samples, and expression of the beta-oxidation gene CPT1A was negatively associated with muscle quality in cachectic patients. Mechanistically, mitochondrial defects result from reduced muscle insulin signalling, downstream of tumour-secreted insulin growth factor binding protein (IGFBP) homologue ImpL2. Strikingly, muscle-specific inhibition of Forkhead box O (FOXO), mitochondrial fusion, or beta-oxidation in tumour-bearing animals preserved muscle integrity. Finally, dietary supplementation with nicotinamide or lipids, improved muscle health in tumour-bearing animals. Overall, our work demonstrates that muscle FOXO, mitochondria dynamics/beta-oxidation and lipid utilisation are key regulators of muscle wasting in cancer cachexia.

A Pipeline for Dynamic Analysis of Mitochondrial Content in Developing T Cells: Bridging the Gap Between High-Throughput Flow Cytometry and Single-Cell Microscopy Analysis

Analyzing the dynamics of mitochondrial content in developing T cells is crucial for understanding the metabolic state during T cell development. However, monitoring mitochondrial content in real-time needs a balance of cell viability and image resolution. In this chapter, we present experimental protocols for measuring mitochondrial content in developing T cells using three modalities: bulk analysis via flow cytometry, volumetric imaging in laser scanning confocal microscopy, and dynamic live-cell monitoring in spinning disc confocal microscopy. Next, we provide an image segmentation and centroid tracking-based analysis pipeline for automated quantification of a large number of microscopy images. These protocols together offer comprehensive approaches to investigate mitochondrial dynamics in developing T cells, enabling a deeper understanding of their metabolic processes.

E-cadherin in developing murine T cells controls spindle alignment and progression through β-selection

A critical stage of T cell development is β-selection; at this stage, the T cell receptor β (TCRβ) chain is generated, and the developing T cell starts to acquire antigenic specificity. Progression through β-selection is assisted by low-affinity interactions between the nascent TCRβ chain and peptide presented on stromal major histocompatibility complex and cues provided by the niche. In this study, we identify a cue within the developing T cell niche that is critical for T cell development. E-cadherin mediates cell-cell interactions and influences cell fate in many developmental systems. In developing T cells, E-cadherin contributed to the formation of an immunological synapse and the alignment of the mitotic spindle with the polarity axis during division, which facilitated subsequent T cell development. Collectively, these data suggest that E-cadherin facilitates interactions with the thymic niche to coordinate the β-selection stage of T cell development.

Scribble and E-cadherin cooperate to control symmetric daughter cell positioning by multiple mechanisms

The fate of the two daughter cells is intimately connected to their positioning, which is in turn regulated by cell junction remodelling and orientation of the mitotic spindle. How multiple cues are integrated to dictate the ultimate positioning of daughters is not clear. Here, we identify novel mechanisms of regulation of daughter positioning in single MCF10A cells. The polarity protein, Scribble cooperates with E-cadherin for sequential roles in daughter positioning. First Scribble stabilises E-cadherin at the mitotic cortex as well as the retraction fibres, to mediate spindle orientation. Second, Scribble re-locates to the junction between the two daughters to allow a new E-cadherin-based-interface to form between them, influencing the width of the nascent daughter-daughter junction and subsequent cell positioning. Thus, E-cadherin and Scribble dynamically relocate to different intracellular sites during cell division to orient the mitotic spindle and control placement of the daughter cells after cell division. This article has an associated First Person interview with the first author of the paper.

Stepwise progression of β-selection during T cell development involves histone deacetylation

During T cell development, the first step in creating a unique T cell receptor (TCR) is genetic recombination of the TCRβ chain. The quality of the new TCRβ is assessed at the β-selection checkpoint. Most cells fail this checkpoint and die, but the coordination of fate at the β-selection checkpoint is not yet understood. We shed new light on fate determination during β-selection using a selective inhibitor of histone deacetylase 6, ACY1215. ACY1215 disrupted the β-selection checkpoint. Characterising the basis for this disruption revealed a new, pivotal stage in β-selection, bookended by up-regulation of TCR co-receptors, CD28 and CD2, respectively. Within this "DN3b^Pre" stage, CD5 and Lef1 are up-regulated to reflect pre-TCR signalling, and their expression correlates with proliferation. These findings suggest a refined model of β-selection in which a coordinated increase in expression of pre-TCR, CD28, CD5 and Lef1 allows for modulating TCR signalling strength and culminates in the expression of CD2 to enable exit from the β-selection checkpoint.

Establishing a multiplex imaging panel to study T cell development in the thymus in mouse

Multiplexed immunohistochemistry enables analysis of cellular and signaling events in the context of an intact organ. Here, we describe protocols for applying multiplexed immunohistochemistry to the mouse thymus. In particular, we describe how to identify cells at the specific differentiation stage known as β-selection, and to monitor pre-TCR signaling and the cellular response at that stage.

For complete details on the use and execution of this protocol, please refer to Allam et al. (2021).

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Establishing a multiplex imaging panel

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Using multiplex imaging to delineate spatial characteristics of developing T cells

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Integrating positional information with differentiation and signalling

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Developing T cells form an immunological synapse for passage through the β-selection checkpoint

The β-selection checkpoint of T cell development tests whether the cell has recombined its genomic DNA to produce a functional T cell receptor β (TCRβ). Passage through the β-selection checkpoint requires the nascent TCRβ protein to mediate signaling through a pre-TCR complex. In this study, we show that developing T cells at the β-selection checkpoint establish an immunological synapse in in vitro and in situ, resembling that of the mature T cell. The immunological synapse is dependent on two key signaling pathways known to be critical for the transition beyond the β-selection checkpoint, Notch and CXCR4 signaling. In vitro and in situ analyses indicate that the immunological synapse promotes passage through the β-selection checkpoint. Collectively, these data indicate that developing T cells regulate pre-TCR signaling through the formation of an immunological synapse. This signaling platform integrates cues from Notch, CXCR4, and MHC on the thymic stromal cell to allow transition beyond the β-selection checkpoint.

The use of the Performance Diagnostic Checklist-Human Services in development of interventions to increase fidelity

Children with Autism Spectrum Disorder (ASD) and other Developmental Disabilities (DD) often have deficits in social, play, and language which often require substantial support to develop the skills. Caregivers and educators are often tasked with developing these skills and working to transfer those acquired skill sets across settings and people (i.e. parents, day care workers, family members). Oftentimes, these naturally occurring skills are more challenging to teach since they require ongoing attention, interaction, and skill promotion from the educators and caregivers. As a result, these skills are sometimes underdeveloped or not worked on as frequently, which in turn, presents greater hardships on families and caregivers. The current study used a multiple treatment design to evaluate the efficacy of three different interventions on promoting and maintaining staff to client interactions during breaks. Treatment one included the antecedent intervention of posted rules; treatment two included the consequence intervention of posted graphical data; the final treatment was a function based treatment (based upon the results of the PDC-HS) which included direct manipulation of immediate consequences for staff to client interactions. Results showed that staff performed at a higher, and more consistent rate, when the treatment was function-based and directly/immediately related to their behavior. This simple manipulation shows promise in promoting the development of staff and family responses that are needed to enhance skill sets that are sometimes more challenging, yet necessary, to develop.

Maps of variability in cell lineage trees

New approaches to lineage tracking have allowed the study of differentiation in multicellular organisms over many generations of cells. Understanding the phenotypic variability observed in these lineage trees requires new statistical methods. Whereas an invariant cell lineage, such as that for the nematode Caenorhabditis elegans, can be described by a lineage map, defined as the pattern of phenotypes overlaid onto the binary tree, a traditional lineage map is static and does not describe the variability inherent in the cell lineages of higher organisms. Here, we introduce lineage variability maps which describe the pattern of second-order variation in lineage trees. These maps can be undirected graphs of the partial correlations between every lineal position, or directed graphs showing the dynamics of bifurcated patterns in each subtree. We show how to infer these graphical models for lineages of any depth from sample sizes of only a few pedigrees. This required developing the generalized spectral analysis for a binary tree, the natural framework for describing tree-structured variation. When tested on pedigrees from C. elegans expressing a marker for pharyngeal differentiation potential, the variability maps recover essential features of the known lineage map. When applied to highly-variable pedigrees monitoring cell size in T lymphocytes, the maps show that most of the phenotype is set by the founder naive T cell. Lineage variability maps thus elevate the concept of the lineage map to the population level, addressing questions about the potency and dynamics of cell lineages and providing a way to quantify the progressive restriction of cell fate with increasing depth in the tree.

A new role for Notch in the control of polarity and asymmetric cell division of developing T cells

A fundamental question in biology is how single cells can reliably produce progeny of different cell types. Notch signalling frequently facilitates fate determination. Asymmetric cell division (ACD) often controls segregation of Notch signalling by imposing unequal inheritance of regulators of Notch. Here, we assessed the functional relationship between Notch and ACD in mouse T cell development. To attain immunological specificity, developing T cells must pass through a pivotal stage termed β-selection, which involves Notch signalling and ACD. We assessed functional interactions between Notch1 and ACD during β-selection using direct presentation of Notch ligands, DL1 and DL4, and pharmacological inhibition of Notch signalling. Contrary to prevailing models, we demonstrate that Notch controls the distribution of Notch1 itself and cell fate determinants, α-Adaptin and Numb. Further, Notch and CXCR4 signalling cooperated to drive polarity during division. Thus, Notch signalling directly orchestrates ACD, and Notch1 is differentially inherited by sibling cells.

Context-Specific Mechanisms of Cell Polarity Regulation

Cell polarity is an essential process shared by almost all animal tissues. Moreover, cell polarity enables cells to sense and respond to the cues provided by the neighboring cells and the surrounding microenvironment. These responses play a critical role in regulating key physiological processes, including cell migration, proliferation, differentiation, vesicle trafficking and immune responses. The polarity protein complexes regulating these interactions are highly evolutionarily conserved between vertebrates and invertebrates. Interestingly, these polarity complexes interact with each other and key signaling pathways in a cell-polarity context-dependent manner. However, the exact mechanisms by which these interactions take place are poorly understood. In this review, we will focus on the roles of the key polarity complexes SCRIB, PAR and Crumbs in regulating different forms of cell polarity, including epithelial cell polarity, cell migration, asymmetric cell division and the T-cell immunological synapse assembly and signaling.

Abstract P5-14-03: Withdrawn

This abstract was withdrawn by the authors.

Potential of saprophage Diptera to acquire culturable livestock-associated antibiotic-resistant bacteria

The increasing prevalence of antibiotic resistance among bacteria is one of the most intractable challenges in 21st-century public health. Dipterans that associate with livestock, livestock waste products and cadavers have the potential to acquire livestock-associated antibiotic-resistant bacteria (LA-ARB) and transmit them to humans. In this study, piglet cadavers were used to attract saprophage dipterans from the environment and those dipterans were sampled for the presence of LA-ARB. In the first trial, culturable microbes resistant to both aminoglycoside and β-lactam antibiotics were found in all cadavers and masses of dipteran larvae, and in three-quarters of adult dipterans. In the second trial, over 130 culturable bacterial colonies resistant to β-lactams were isolated from the cadavers, larval and adult dipterans. Over 100 of those colonies were coliform or metabolically similar bacteria. Adult dipterans carried β-lactam resistant staphylococci, whereas those bacterial types were absent from larval dipterans and cadavers, suggesting they were picked up from elsewhere in the environment. This research indicates that LA-ARB are ubiquitous in pig farms, and dipterans have the potential to carry medically important microbes. Further research is encouraged to determine the extent to which dipterans acquire microbes from animal agriculture relative to other environments.

Chitosan-coated amyloid fibrils increase adipogenesis of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have the potential to revolutionize medicine due to their ability to differentiate into specific lineages for targeted tissue repair. Development of materials and cell culture platforms that improve differentiation of either autologous or allogenic stem cell sources into specific lineages would enhance clinical utilization of MCSs. In this study, nanoscale amyloid fibrils were evaluated as substrate materials to encourage viability, proliferation, multipotency, and differentiation of MSCs. Fibrils assembled from the proteins lysozyme or β-lactoglobulin, with and without chitosan coatings, were deposited on planar mica surfaces. MSCs were cultured and differentiated on fibril-covered surfaces, as well as on unstructured controls and tissue culture plastic. Expression of CD44 and CD90 proteins indicated that multipotency was maintained for all fibrils, and osteogenic differentiation was similarly comparable among all tested materials. MSCs grown for 7days on fibril-covered surfaces favored multicellular spheroid formation and demonstrated a >75% increase in adipogenesis compared to tissue culture plastic controls, although this benefit could only be achieved if MSCs were transferred to TCP for the final differentiation step. The largest spheroids and greatest tendency to undergo adipogenesis was evidenced among MSCs grown on fibrils coated with the positively-charged polysaccharide chitosan, suggesting that spheroid formation is prompted by both topography and cell-surface interactivity and that there is a connection between multicellular spheroid formation and adipogenesis.

The Asymmetric Cell Division Regulators Par3, Scribble and Pins/Gpsm2 Are Not Essential for Erythroid Development or Enucleation

Erythroid enucleation is the process by which the future red blood cell disposes of its nucleus prior to entering the blood stream. This key event during red blood cell development has been likened to an asymmetric cell division (ACD), by which the enucleating erythroblast divides into two very different daughter cells of alternate molecular composition, a nucleated cell that will be removed by associated macrophages, and the reticulocyte that will mature to the definitive erythrocyte. Here we investigated gene expression of members of the Par, Scribble and Pins/Gpsm2 asymmetric cell division complexes in erythroid cells, and functionally tested their role in erythroid enucleation in vivo and ex vivo. Despite their roles in regulating ACD in other contexts, we found that these polarity regulators are not essential for erythroid enucleation, nor for erythroid development in vivo. Together our results put into question a role for cell polarity and asymmetric cell division in erythroid enucleation.

Imaging Asymmetric T Cell Division

Asymmetric cell division (ACD) controls cell fate decisions in model organisms such as Drosophila and C. elegans and has recently emerged as a mediator of T cell fate and hematopoiesis. The most appropriate methods for assessing ACD in T cells are still evolving. Here we describe the methods currently applied to monitor and measure ACD of developing and activated T cells. We provide an overview of approaches for capturing cells in the process of cytokinesis in vivo, ex vivo, or during in vitro culture. We provide methods for in vitro fixed immunofluorescent staining and for time-lapse analysis. We provide an overview of the different approaches for quantification of ACD of lymphocytes, discuss the pitfalls and concerns in interpretation of these analyses, and provide detailed methods for the quantification of ACD in our group.

Dense small molecule labeling enables activator-dependent STORM by proximity mapping

Stochastic optical reconstruction microscopy (STORM) enables high-resolution imaging, but multi-channel 3D imaging is problematic because of chromatic aberrations and alignment errors. The use of activator-dependent STORM in which spectrally distinct activators can be coupled with a single reporter can circumvent such issues. However, the standard approach of linking activators and reporters to a single antibody molecule is hampered by low labeling density and the large size of the antibody. We proposed that small molecule labels might enable activator-dependent STORM if the reporter or activator were linked to separate small molecules that bound within 3.5 nm of each other. This would greatly increase the labeling density and therefore improve resolution. We tested various mixtures of phalloidin- or mCling-conjugated fluorophore to demonstrate this feasibility. The specific activation was dependent on the choice of activator, its density, a matching activating laser and its power. In addition to providing an effective means of multi-channel 3D STORM imaging, this method also provides information about the local proximity between labels, potentially enabling super-resolved mapping of the conformation of the labeled structures.

Calcium Signaling Is Required for Erythroid Enucleation

Although erythroid enucleation, the property of erythroblasts to expel their nucleus, has been known for 7ore than a century, surprisingly little is known regarding the molecular mechanisms governing this unique developmental process. Here we show that similar to cytokinesis, nuclear extrusion requires intracellular calcium signaling and signal transduction through the calmodulin (CaM) pathway. However, in contrast to cytokinesis we found that orthochromatic erythroblasts require uptake of extracellular calcium to enucleate. Together these functional studies highlight a critical role for calcium signaling in the regulation of erythroid enucleation.

Asymmetric cell division during T cell development controls downstream fate

T cell precursors undergo asymmetric cell division after T cell receptor genomic recombination, with stromal cell cues controlling the differential inheritance of fate determinants Numb and α-Adaptin by the daughters of a dividing DN3a T cell precursor.

During mammalian T cell development, the requirement for expansion of many individual T cell clones, rather than merely expansion of the entire T cell population, suggests a possible role for asymmetric cell division (ACD). We show that ACD of developing T cells controls cell fate through differential inheritance of cell fate determinants Numb and α-Adaptin. ACD occurs specifically during the β-selection stage of T cell development, and subsequent divisions are predominantly symmetric. ACD is controlled by interaction with stromal cells and chemokine receptor signaling and uses a conserved network of polarity regulators. The disruption of polarity by deletion of the polarity regulator, Scribble, or the altered inheritance of fate determinants impacts subsequent fate decisions to influence the numbers of DN4 cells arising after the β-selection checkpoint. These findings indicate that ACD enables the thymic microenvironment to orchestrate fate decisions related to differentiation and self-renewal.

A Chemical Screening Approach to Identify Novel Key Mediators of Erythroid Enucleation

Erythroid enucleation is critical for terminal differentiation of red blood cells, and involves extrusion of the nucleus by orthochromatic erythroblasts to produce reticulocytes. Due to the difficulty of synchronizing erythroblasts, the molecular mechanisms underlying the enucleation process remain poorly understood. To elucidate the cellular program governing enucleation, we utilized a novel chemical screening approach whereby orthochromatic cells primed for enucleation were enriched ex vivo and subjected to a functional drug screen using a 324 compound library consisting of structurally diverse, medicinally active and cell permeable drugs. Using this approach, we have confirmed the role of HDACs, proteasomal regulators and MAPK in erythroid enucleation and introduce a new role for Cyclin-dependent kinases, in particular CDK9, in this process. Importantly, we demonstrate that when coupled with imaging analysis, this approach provides a powerful means to identify and characterize rate limiting steps involved in the erythroid enucleation process.

Lethal giant larvae-1 deficiency enhances the CD8(+) effector T-cell response to antigen challenge in vivo

Lethal giant larvae-1 (Lgl-1) is an evolutionary conserved protein that regulates cell polarity in diverse lineages; however, the role of Lgl-1 in the polarity and function of immune cells remains to be elucidated. To assess the role of Lgl-1 in T cells, we generated chimeric mice with a hematopoietic system deficient for Lgl-1. Lgl-1 deficiency did not impair the activation or function of peripheral CD8(+) T cells in response to antigen presentation in vitro, but did skew effector and memory T-cell differentiation. When challenged with antigen-expressing virus or tumor, Lgl-1-deficient mice displayed altered T-cell responses. This manifested in a stronger antiviral and antitumor effector CD8(+) T-cell response, the latter resulting in enhanced control of MC38-OVA tumors. These results reveal a novel role for Lgl-1 in the regulation of virus-specific T-cell responses and antitumor immunity.

Normalized polarization ratios for the analysis of cell polarity

The quantification and analysis of molecular localization in living cells is increasingly important for elucidating biological pathways, and new methods are rapidly emerging. The quantification of cell polarity has generated much interest recently, and ratiometric analysis of fluorescence microscopy images provides one means to quantify cell polarity. However, detection of fluorescence, and the ratiometric measurement, is likely to be sensitive to acquisition settings and image processing parameters. Using imaging of EGFP-expressing cells and computer simulations of variations in fluorescence ratios, we characterized the dependence of ratiometric measurements on processing parameters. This analysis showed that image settings alter polarization measurements; and that clustered localization is more susceptible to artifacts than homogeneous localization. To correct for such inconsistencies, we developed and validated a method for choosing the most appropriate analysis settings, and for incorporating internal controls to ensure fidelity of polarity measurements. This approach is applicable to testing polarity in all cells where the axis of polarity is known.

Polarized cells, polarized views: asymmetric cell division in hematopoietic cells

It has long been recognized that alterations in cell shape and polarity play important roles in coordinating lymphocyte functions. In the last decade, a new aspect of lymphocyte polarity has attracted much attention, termed asymmetric cell division (ACD). ACD has previously been shown to dictate or influence many aspects of development in model organisms such as the worm and the fly, and to be disrupted in disease. Recent observations that ACD also occurs in lymphocytes led to exciting speculations that ACD might influence lymphocyte differentiation and function, and leukemia. Dissecting the role that ACD might play in these activities has not been straightforward, and the evidence to date for a functional role in lymphocyte fate determination has been controversial. In this review, we discuss the evidence to date for ACD in lymphocytes, and how it might influence lymphocyte fate. We also discuss current gaps in our knowledge, and suggest approaches to definitively test the physiological role of ACD in lymphocytes.

Lethal giant larvae 1 tumour suppressor activity is not conserved in models of mammalian T and B cell leukaemia

In epithelial and stem cells, lethal giant larvae (Lgl) is a potent tumour suppressor, a regulator of Notch signalling, and a mediator of cell fate via asymmetric cell division. Recent evidence suggests that the function of Lgl is conserved in mammalian haematopoietic stem cells and implies a contribution to haematological malignancies. To date, direct measurement of the effect of Lgl expression on malignancies of the haematopoietic lineage has not been tested. In Lgl1^−/− mice, we analysed the development of haematopoietic malignancies either alone, or in the presence of common oncogenic lesions. We show that in the absence of Lgl1, production of mature white blood cell lineages and long-term survival of mice are not affected. Additionally, loss of Lgl1 does not alter leukaemia driven by constitutive Notch, c-Myc or Jak2 signalling. These results suggest that the role of Lgl1 in the haematopoietic lineage might be restricted to specific co-operating mutations and a limited number of cellular contexts.

Establishment and characterization of a new human extragonadal germ cell line, SEM-1, and its comparison with TCam-2 and JKT-1

OBJECTIVE

To describe the establishment and characterization of a human cell line, SEM-1, from a patient diagnosed with a mediastinal seminoma.

METHODS

A small percentage of germ cell tumors develop as primary lesions in extragonadal sites, and the etiology of these tumors is poorly understood. Currently, only 2 cell lines from seminoma patients have been reported, JKT-1 and TCam-2, both derived from the testis. The cell line was characterized by heterotransplantation in Nude mice, cytogenetic studies, immunohistochemical and flow cytometry staining for germ cell tumor biomarkers, quantitative reverse-transcription polymerase chain reaction for cancer testis antigen expression, and BRAF mutation screening with quantitative polymerase chain reaction.

RESULTS

Characterization studies confirmed the human extragonadal seminoma origin of SEM-1 and demonstrated that it had more features in common with TCam-2 than JKT-1. Specifically, SEM-1 was positive for Sal-like protein 4 (SALL-4), activator protein-2γ (AP-2γ), and cytokeratin CAM5.2, and demonstrated heterogeneous expression of stem cell markers octamer-binding transcription factor 3/4, NANOG, c-KIT, SOX17, and SOX2. Cytogenetic analysis revealed a hypotriploid chromosome number, with multiple copies of 12p, but isochromosome 12p and the BRAF mutation V600E were not identified. The cell lines also did not contain the BRD4/NUT gene rearrangement [t(15,19)] seen in midline carcinomas nor did they contain overexpressed nuclear protein in testis (NUT) genes.

CONCLUSION

SEM-1 is the first cell line derived from an extragonadal germ cell tumor showing intermediate characteristics between seminoma and nonseminoma, and as such, is an important model to study the molecular pathogenesis of this malignancy.

Immune cell infiltration patterns and survival in head and neck squamous cell carcinoma

PURPOSE

This study examines the tumour-host immune interactions in head and neck squamous cell carcinoma (HNSCC) and their relationship to human papillomavirus (HPV) infectivity and patient survival.

METHODS

The adaptive and innate immune profile of surgical tumour specimens obtained from HNSCC patients was determined using qRT-PCR and immunohistochemistry. Intratumoural and invading margin leukocyte populations (CD3, CD8, CD16, CD20, CD68, FoxP3 and HLA-DR) were quantified and compared with patient disease-specific survival. Additionally, the expression of 41 immune activation- and suppression-related genes was evaluated in the tumour microenvironment. Tumour cells were also assessed for expression of HLA-A, HLA-G and HLA-DR. HPV infectivity of tumour biopsies was determined using HPV consensus primers (MY09/MY11 and GP5+/GP6+) and confirmed with p16 immunohistochemistry.

RESULTS

HPV+ patient samples showed a significantly increased infiltration by intratumoural CD20+ B cells, as well as by invasive margin FoxP3+Treg, compared with HPV- patient samples. There was also a trend towards increased intratumoural CD8+ T cells and HLA-G expression on tumour cells in HPV+ samples. qRT-PCR data demonstrated a general pattern of increased immune activation and suppression mechanisms in HPV+ samples. Additionally, a combined score of intratumoural and invasive margin FoxP3 infiltration was significantly associated with disease-specific survival (P < 0.05).

CONCLUSIONS

These data demonstrate significant differences in the immune cell profile of HPV+ and HPV- HNSCC. This study identifies several possible targets for immunotherapy and possible prognostic markers (FoxP3 and HLA-G) that may be specific to HNSCC.

Characterization of in vivo Dlg1 deletion on T cell development and function

Background

The polarized reorganization of the T cell membrane and intracellular signaling molecules in response to T cell receptor (TCR) engagement has been implicated in the modulation of T cell development and effector responses. In siRNA-based studies Dlg1, a MAGUK scaffold protein and member of the Scribble polarity complex, has been shown to play a role in T cell polarity and TCR signal specificity, however the role of Dlg1 in T cell development and function in vivo remains unclear.

Methodology/Principal Findings

Here we present the combined data from three independently-derived dlg1-knockout mouse models; two germline deficient knockouts and one conditional knockout. While defects were not observed in T cell development, TCR-induced early phospho-signaling, actin-mediated events, or proliferation in any of the models, the acute knockdown of Dlg1 in Jurkat T cells diminished accumulation of actin at the IS. Further, while Th1-type cytokine production appeared unaffected in T cells derived from mice with a dlg1germline-deficiency, altered production of TCR-dependent Th1 and Th2-type cytokines was observed in T cells derived from mice with a conditional loss of dlg1 expression and T cells with acute Dlg1 suppression, suggesting a differential requirement for Dlg1 activity in signaling events leading to Th1 versus Th2 cytokine induction. The observed inconsistencies between these and other knockout models and siRNA strategies suggest that 1) compensatory upregulation of alternate gene(s) may be masking a role for dlg1 in controlling TCR-mediated events in dlg1 deficient mice and 2) the developmental stage during which dlg1 ablation begins may control the degree to which compensatory events occur.

Conclusions/Significance

These findings provide a potential explanation for the discrepancies observed in various studies using different dlg1-deficient T cell models and underscore the importance of acute dlg1 ablation to avoid the upregulation of compensatory mechanisms for future functional studies of the Dlg1 protein.

Abstract 3669: Autocrine interleukin/STAT3 signaling in breast implant-associated T cell anaplastic large cell lymphoma cell lines suggests a mechanism for tumor progression and effective therapy

Recently, over 80 cases of anaplastic large-cell kinase (ALK)-negative, T-cell, anaplastic, non-Hodgkin lymphomas (T-ALCL) have been identified worldwide in patients with textured saline and silicone breast implants. These breast implant-associated T-ALCL cases are striking for their homogeneous clinical presentation and pathology that is distinct from established classes of ALCL. In order to understand the nature of this newly emerged clinical entity, we have established three new cell lines, designated T cell Breast Lymphoma (TLBR) -1, -2, and -3, from patient primary tumor biopsy specimens. Characterization of these pre-clinical models confirmed fidelity to the original tumor biopsy specimens and highlighted unique features that may aid the development of effective treatments for these cancers. Gene expression analysis demonstrated significant up-regulation of survivin and down-regulation of pro-apoptotic genes (BID, BAK, BBC3) by all TLBR cell lines relative to healthy donor T cells. This preliminary finding prompted examination of upstream regulators of cell survival in T cells, namely the interleukin signaling associated with the JAK/STAT pathway. TLBR cell lines were found to secrete high levels of IL-6 and IL-10, and were strongly positive for the cognate receptors. The TLBR cell lines also showed elevated levels of STAT3 and pSTAT3 by immunoblotting techniques, along with a simultaneous reduction in expression of the pSTAT3 phosphatase, SHP-1. These results implicate an unregulated autocrine STAT3 pathway present in the TLBR cell lines that strongly contributes to their tumorigenesis. Assays of various inhibitors of this pathway support this hypothesis since targeting of STAT3 with the tyrosine kinase inhibitor, Sunitinib, led to dramatic in vitro cell death in all TLBR cell lines. More specific inhibition of STAT3 with S3I-201 had comparable results with Sunitinib. Furthermore, IL-6 neutralization by a monoclonal antibody or SHP-1 restoration by 5-azacytidine treatment also demonstrated moderate efficacy in inhibiting TLBR cell line growth in vitro. These discoveries strongly suggest the use of these reagents in the clinical treatment of Breast Implant Associated T-ALCL. The TLBR cell lines closely resemble the primary breast implant-associated lymphomas from which they were derived, and as such provide valuable preclinical models to study the unique biology and provide clinicians with improved knowledge for treatment and diagnosis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3669. doi:1538-7445.AM2012-3669

Abstract 3550: Differences in immune escape in HPV+ versus HPV- head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the 6th most common cancer worldwide and has not seen an improvement in survival in decades. Current standard-of-care treatments including surgical resection, chemotherapy and radiation still lead to high rates of recurrence and loco-regional metastasis contributing to the poor prognosis in these patients. It is well established that HNSCC are highly immune-modulatory tumors and may therefore benefit from immunotherapy treatment regimens. Better methods are therefore needed to match patients with the appropriate immunotherapy. Recently, human papillomavirus (HPV) was implicated in the etiology of a subset of HNSCC arising in younger patients without a history of alcohol and tobacco use. Approximately 30% of HNSCC tumors are HPV+ and despite late stage presentation, often have a better prognosis and response to therapy. This study examines how host immune recognition and response varies between HPV+ and HPV- HNSCC, with the goal of identifying new targets for immunotherapy. The immune profile and HPV infection status of 41 HNSCC patient tumor samples obtained from surgical resection was characterized by qRT-PCR, PCR, and IHC techniques. Tumor samples were analyzed for the expression of 40 genes involved in immune activation and suppression in the tumor microenvironment to generate an immune profile. Gene expression levels were normalized to GAPDH and compared across HPV+, HPV- and normal tissue groups by ANOVA and post-test pairwise analysis. HPV infectivity of tumor biopsies was determined using HPV consensus primers (MY09/MY11 and GP5+/GP6+) and confirmed with p16 immunohistochemistry. From these studies, eight of 41 (20%) HNSCC biopsies were HPV+ by PCR and IHC analysis. HPV+ tumors demonstrated statistically significant increased expression of genes related to immunosuppression including regulatory T (CD4, FoxP3, CTLA-4, and FasL) and myeloid suppressor cell markers (CD11b and IL-6, an inducer of these suppressor cells), as well as negative-regulators (SOCS1) (p&lt;0.05). These tumors also demonstrated an increase in markers of immune activation and infiltration, including evidence of T cells (CD4, Fas-L), antigen presenting cells (CD80, CD83, CD1c), and inflammatory cytokines and co-stimulatory molecules (IL-2, IL-12, IFN- γ, and OX40L) (p&lt;0.05). There were no statistically significant differences in gene expression found between normal tissue and HPV- HNSCC tumors. These studies demonstrate a general pattern of increased immunogenicity and concurrent immunosuppression in patients with HPV+ versus HPV- HNSCC that could potentially be used to inform immunotherapy treatment of HNSCC patients. HPV+ tumors may be more effectively treated with a regimen that employs a combination of immune stimulation and reversal of immune tolerance mechanisms, while HPV- tumors may require greater immune stimulation to activate endogenous anti-tumor immune responses.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3550. doi:1538-7445.AM2012-3550

Abstract 1553: Key determinants of immunotherapy success in frequently-used murine tumor models

Cancer immunotherapy uses a patient's own immune system to recognize and eliminate malignant cells. The potential advantages of this approach over conventional treatments include the systemic trafficking of immune cells to treat primary and metastatic disease, inherent antigen-specificity of adaptive immunity to minimize collateral damage, and the induction of immunological memory to prevent recurrent disease. While many acknowledge the promise of immunotherapy, its translation to the clinic has been slow and only occasionally successful. In the more than 3 decades of experience of our laboratory in developing and testing immunotherapy reagents for cancer, we observed that a given set of reagents can produce complete regressions in some but not all tumor models. We hypothesized that a major contributor to this variability was underlying differences in the immune escape strategies utilized by different tumors. Our hypothesis was supported with data from a series of immunotherapy experiments on a panel of experimental murine solid tumor models. Comprehensive immune profiles were generated for each by measuring tumor infiltrating leukocytes (TIL), immune activation, and immune suppression present in the tumor microenvironment using qRT-PCR, immunohistochemistry staining, and flow cytometry techniques. Key differences emerged amongst models in the extent of immune activation that correlated directly with TIL and immunosuppression. From these data, it appears that some tumors are more “visible” to the immune system and have active countermeasures to survive, while others use immune evasion strategies to persist in the host. To classify tumor models along this spectrum, ten immune-related genes and cell markers showing significant change across the models were selected to generate an immunogenicity score for each model: CD40, 41BBL, OX40L, CD80, CD86, CD11c, CD45, BM-2 (PMN marker), Granzyme B, and CD8. Importantly, we observed that MHC class I mouse equivalent H2-D correlated with this immunogenicity level for each tumor. Secondly, Treg and MDSC were measured in the tumor microenvironment and draining lymphoid tissues using immunohistochemical and flow cytometry techniques to determine the dominant suppressor cell population(s) present. Immunotherapy regimens were then developed to match each tumor model using immunogenicity to indicate the level of immune stimulation needed and suppressor cell component to indicate targets for reversing tumor tolerance. These regimens were used to treat established solid tumors in mice and demonstrated that two features of a tumor's immune profile, namely immunogenicity level and dominant suppressor cell component, are the key determinants of immunotherapy success in vivo. Viewed in this way, the tumor/host relationship becomes the overriding feature for determining optimal treatment for patients based upon immune profiling data obtained at the time of biopsy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1553. doi:1538-7445.AM2012-1553

Chemokines, costimulatory molecules and fusion proteins for the immunotherapy of solid tumors

In this article, the role of chemokines and costimulatory molecules in the immunotherapy of experimental murine solid tumors and immunotherapy used in ongoing clinical trials are presented. Chemokine networks regulate physiologic cell migration that may be disrupted to inhibit antitumor immune responses or co-opted to promote tumor growth and metastasis in cancer. Recent studies highlight the potential use of chemokines in cancer immunotherapy to improve innate and adaptive cell interactions and to recruit immune effector cells into the tumor microenvironment. Another critical component of antitumor immune responses is antigen priming and activation of effector cells. Reciprocal expression and binding of costimulatory molecules and their ligands by antigen-presenting cells and naive lymphocytes ensures robust expansion, activity and survival of tumor-specific effector cells in vivo. Immunotherapy approaches using agonist antibodies or fusion proteins of immunomodulatory molecules significantly inhibit tumor growth and boost cell-mediated immunity. To localize immune stimulation to the tumor site, a series of fusion proteins consisting of a tumor-targeting monoclonal antibody directed against tumor necrosis and chemokines or costimulatory molecules were generated and tested in tumor-bearing mice. While several of these reagents were initially shown to have therapeutic value, combination therapies with methods to delete suppressor cells had the greatest effect on tumor growth. In conclusion, a key conclusion that has emerged from these studies is that successful immunotherapy will require both advanced methods of immunostimulation and the removal of immunosuppression in the host.

T cell protein tyrosine phosphatase attenuates T cell signaling to maintain tolerance in mice

Many autoimmune diseases exhibit familial aggregation, indicating that they have genetic determinants. Single nucleotide polymorphisms in PTPN2, which encodes T cell protein tyrosine phosphatase (TCPTP), have been linked with the development of several autoimmune diseases, including type 1 diabetes and Crohn's disease. In this study, we have identified TCPTP as a key negative regulator of TCR signaling, which might explain the association of PTPN2 SNPs with autoimmune disease. We found that TCPTP dephosphorylates and inactivates Src family kinases to regulate T cell responses. Using T cell-specific TCPTP-deficient mice, we established that TCPTP attenuates T cell activation and proliferation in vitro and blunts antigen-induced responses in vivo. TCPTP deficiency lowered the in vivo threshold for TCR-dependent CD8(+) T cell proliferation. Consistent with this, T cell-specific TCPTP-deficient mice developed widespread inflammation and autoimmunity that was transferable to wild-type recipient mice by CD8(+) T cells alone. This autoimmunity was associated with increased serum levels of proinflammatory cytokines and anti-nuclear antibodies, T cell infiltrates in non-lymphoid tissues, and liver disease. These data indicate that TCPTP is a critical negative regulator of TCR signaling that sets the threshold for TCR-induced naive T cell responses to prevent autoimmune and inflammatory disorders arising.

USC-HN2, a new model cell line for recurrent oral cavity squamous cell carcinoma with immunosuppressive characteristics

Head and neck squamous cell carcinomas (HNSCC) are common and aggressive tumors that have not seen an improvement in survival rates in decades. These tumors are believed to evade the immune system through a variety of mechanisms and are therefore highly immune modulatory. In order to elucidate their interaction with the immune system and develop new therapies targeting immune escape, new pre-clinical models are needed. A novel human cell line, USC-HN2, was established from a patient biopsy specimen of invasive, recurrent buccal HNSCC and characterized by morphology, heterotransplantation, cytogenetics, phenotype, gene expression, and immune modulation studies and compared to a similar HNSCC cell line; SCCL-MT1. Characterization studies confirmed the HNSCC origin of USC-HN2 and demonstrated a phenotype similar to the original tumor and typical of aggressive oral cavity HNSCC (EGFR(+)CD44v6(+)FABP5(+)Keratin(+) and HPV(-)). Gene and protein expression studies revealed USC-HN2 to have highly immune-modulatory cytokine production (IL-1β, IL-6, IL-8, GM-CSF, and VEGF) and strong regulatory T and myeloid derived suppressor cell (MDSC) induction capacity in vitro. Of note, both USC-HN2 and SCCL-MT1 were found to have a more robust cytokine profile and MDSC induction capacity when compared to seven previously established HNSCC cell lines. Additionally, microarray gene expression profiling of both cell lines demonstrate up-regulation of antigen presenting genes. Because USC-HN2 is therefore highly immunogenic, it also induces strong immune suppression to evade immunologic destruction. Based upon these results, both cell lines provide an excellent model for the development of new suppressor cell-targeted immunotherapies.

Functional characterization of human Cd33+ and Cd11b+ myeloid-derived suppressor cell subsets induced from peripheral blood mononuclear cells co-cultured with a diverse set of human tumor cell lines

Background

Tumor immune tolerance can derive from the recruitment of suppressor cell populations, including myeloid-derived suppressor cells (MDSC). In cancer patients, MDSC accumulation correlates with increased tumor burden, but the mechanisms of MDSC induction remain poorly understood.

Methods

This study examined the ability of human tumor cell lines to induce MDSC from healthy donor PBMC using in vitro co-culture methods. These human MDSC were then characterized for morphology, phenotype, gene expression, and function.

Results

Of over 100 tumor cell lines examined, 45 generated canonical CD33⁺HLA-DR^lowLineage^- MDSC, with high frequency of induction by cervical, ovarian, colorectal, renal cell, and head and neck carcinoma cell lines. CD33⁺ MDSC could be induced by cancer cell lines from all tumor types with the notable exception of those derived from breast cancer (0/9, regardless of hormone and HER2 status). Upon further examination, these and others with infrequent CD33⁺ MDSC generation were found to induce a second subset characterized as CD11b⁺CD33^lowHLA-DR^lowLineage^-. Gene and protein expression, antibody neutralization, and cytokine-induction studies determined that the induction of CD33⁺ MDSC depended upon over-expression of IL-1β, IL-6, TNFα, VEGF, and GM-CSF, while CD11b⁺ MDSC induction correlated with over-expression of FLT3L and TGFβ. Morphologically, both CD33⁺ and CD11b⁺ MDSC subsets appeared as immature myeloid cells and had significantly up-regulated expression of iNOS, NADPH oxidase, and arginase-1 genes. Furthermore, increased expression of transcription factors HIF1α, STAT3, and C/EBPβ distinguished MDSC from normal counterparts.

Conclusions

These studies demonstrate the universal nature of MDSC induction by human solid tumors and characterize two distinct MDSC subsets: CD33⁺HLA-DR^lowHIF1α⁺/STAT3⁺ and CD11b⁺HLA-DR^lowC/EBPβ⁺, which should enable the development of novel diagnostic and therapeutic reagents for cancer immunotherapy.

Asymmetric proteasome segregation as a mechanism for unequal partitioning of the transcription factor T-bet during T lymphocyte division

Polarized segregation of proteins in T cells is thought to play a role in diverse cellular functions including signal transduction, migration, and directed secretion of cytokines. Persistence of this polarization can result in asymmetric segregation of fate-determining proteins during cell division, which may enable a T cell to generate diverse progeny. Here, we provide evidence that a lineage-determining transcription factor, T-bet, underwent asymmetric organization in activated T cells preparing to divide and that it was unequally partitioned into the two daughter cells. This unequal acquisition of T-bet appeared to result from its asymmetric destruction during mitosis by virtue of concomitant asymmetric segregation of the proteasome. These results suggest a mechanism by which a cell may unequally localize cellular activities during division, thereby imparting disparity in the abundance of cell fate regulators in the daughter cells.

Super-resolution imaging and statistical analysis of CdSe/CdS Core/Shell semiconductor nanocrystals

Here we present a multifunctional algorithm. Firstly a super-resolution method is presented for optically imaging the spatial distribution of semiconductor nanocrystals with nanometre localisation. Secondly highly resolved multiple photoluminescence trajectories of hundreds of single semiconductor nanocrystals are obtained simultaneously.

Asymmetric cell division of T cells upon antigen presentation uses multiple conserved mechanisms

Asymmetric cell division is a potential means by which cell fate choices during an immune response are orchestrated. Defining the molecular mechanisms that underlie asymmetric division of T cells is paramount for determining the role of this process in the generation of effector and memory T cell subsets. In other cell types, asymmetric cell division is regulated by conserved polarity protein complexes that control the localization of cell fate determinants and spindle orientation during division. We have developed a tractable, in vitro model of naive CD8(+) T cells undergoing initial division while attached to dendritic cells during Ag presentation to investigate whether similar mechanisms might regulate asymmetric division of T cells. Using this system, we show that direct interactions with APCs provide the cue for polarization of T cells. Interestingly, the immunological synapse disseminates before division even though the T cells retain contact with the APC. The cue from the APC is translated into polarization of cell fate determinants via the polarity network of the Par3 and Scribble complexes, and orientation of the mitotic spindle during division is orchestrated by the partner of inscuteable/G protein complex. These findings suggest that T cells have selectively adapted a number of evolutionarily conserved mechanisms to generate diversity through asymmetric cell division.

Upsides and downsides to polarity and asymmetric cell division in leukemia

The notion that polarity regulators can act as tumor suppressors in epithelial cells is now well accepted. The function of these proteins in lymphocytes is less well explored, and their possible function as suppressors of leukemia has had little attention so far. We review the literature on lymphocyte polarity and the growing recognition that polarity proteins have an important function in lymphocyte function. We then describe molecular relationships between the polarity network and signaling pathways that have been implicated in leukemogenesis, which suggest mechanisms by which the polarity network might impact on leukemogenesis. We particularly focus on the possibility that disruption of polarity might alter asymmetric cell division (ACD), and that this might be a leukemia-initiating event. We also explore the converse possibility that leukemic stem cells might be produced or maintained by ACD, and therefore that Dlg, Scribble and Lgl might be important regulators of this process.

The effect of an acidic, copper sulfate-based commercial sanitizer on indicator, pathogenic, and spoilage bacteria associated with broiler chicken carcasses when applied at various intervention points during poultry processing

Studies were conducted to evaluate 1) the effect of an acidic, copper sulfate-based commercial sanitizer on pathogenic, indicator, and spoilage bacteria in a model scalder system, 2) the effect of this sanitizer on total aerobic bacteria (APC) and Escherichia coli counts, and Salmonella prevalence on broiler chicken carcasses when applied during scalding or scalding and postpick dipping, and 3) the ability of sanitizer to extend the shelf-life of broiler chicken carcasses. Exposure of Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, Pseudomonas fluorescens, or Shewanella putrefaciens to the sanitizer in scalder water at 54 degrees C for 2 min resulted in complete elimination of these bacterial species. Exposure of E. coli to the treated scald water resulted in a 4.9 log(10) reduction. These data suggest that this sanitizer would be effective for use in scalders. When applied during scalding in a commercial processing plant, APC and E. coli counts were significantly (P <or= 0.05) reduced on all days of sampling. The average log10 reduction overall was 3.80 and 3.05 for APC and E. coli, respectively. Salmonella prevalence was reduced by an average of 30%. For carcasses that were scalded, picked, and dipped postpick using this sanitizer, APC were significantly P <or= 0.05) reduced on all days of sampling by an average of 1.19 log10. Escherichia coli counts were reduced on all but 2 d of sampling for carcasses scalded, picked, and dipped in this sanitizer, except for d 2 and 10. Averages on these days were higher for controls, but were not significantly different. Salmonella prevalence was not consistently impacted overall. For the shelf-life study, odor scores were significantly (P <or= 0.05) reduced for treated carcasses at d 8 through 14 of storage. The psychrotrophic plate counts were significantly (P <or= 0.05) lower on treated carcasses at d 6 through 14 of storage. This sanitizer suppressed spoilage bacteria with a 99.99% reduction at d 10 and a 99.9% reduction at d 12 of storage. This effect could result in an extension of the shelf life of the poultry carcasses by up to 4 d.

Coordination of protein synthesis and degradation

The degree of coordination between protein synthesis and protein degradation in developing and mature cels is considered. Studies on specific enzyme and general protein turnover in developing liver and differentiating mammary gland are presented. In the mature liver mitochondrion average protein degradation rates are higher for outer membrane and intermembrane space proteins than for matrix and inner membrane proteins. Significant heterogeneity of protein degradation rates was observed only in the outer mitochondrial membrane. During postnatal development the rates of degradation of proteins in many liver cellular fractions are increased. In the mitochondrion only the average rates of degradation of proteins in the outer membrane and intermembrane space fractions increase during development. Evidence for hormonally regulated changes in both protein synthesis and degradation during mammary cell differentiation is given. The data indicate that a transitory decrease in protein degradation accompanies the increase in protein synthesis on hormonal stimulation of the tissue. The results from the two model systems are collated and used to formulate a phenomenological hypothesis of protein degradation and its integration with protein synthesis in steady-state and non-steady-state conditions.

Structure-function analysis of the determinants of CD46 polarization in T cells-combined role for polarity proteins,lipid rafts and ERM proteins (87.19)

CD46 is a ubiquitously expressed human cell surface protein that acts as a receptor for complements for various pathogens including the measles virus. We demonstrated that ligation of the immunoregulatory cell surface receptor, CD46, altered T cell polarity and impaired activation and effector function in response to TCR or NK cell receptor signalling. However the molecular mechanisms by which T cell function is inhibited are not known.

We have previously shown that CD46 binds to the polarity protein, Discs large (Dlg), and that this interaction is important for the polarized localization of CD46. Specifically, CD46 localizes to the uropod of T cells, and to the distal pole of T cells undergoing antigen presentation. Polarization of CD46 is partially reduced by mutation of the Dlg-binding site, and is also partially reduced by mutation of the Cysteine residue in the transmembrane domain that is palmitoylated to allow association of CD46 with lipid rafts. However, comparison of CD46 mutants suggests that other determinants are also important in CD46 polarization. We hypothesize that the ERM proteins interacts with CD46, regulates its polarization in T cells, and perhaps play a role in CD46 signal transduction. To assess this we have generated mutations in the ERM-binding consensus sequences of CD46 and expressed these mutants in a uropod-containing T cell line for functional characterization. These studies will help to elucidate the molecular mechanisms by which CD46 exerts its immunoregulatory effects.

Asymmetric T lymphocyte division in the initiation of adaptive immune responses

A hallmark of mammalian immunity is the heterogeneity of cell fate that exists among pathogen-experienced lymphocytes. We show that a dividing T lymphocyte initially responding to a microbe exhibits unequal partitioning of proteins that mediate signaling, cell fate specification, and asymmetric cell division. Asymmetric segregation of determinants appears to be coordinated by prolonged interaction between the T cell and its antigen-presenting cell before division. Additionally, the first two daughter T cells displayed phenotypic and functional indicators of being differentially fated toward effector and memory lineages. These results suggest a mechanism by which a single lymphocyte can apportion diverse cell fates necessary for adaptive immunity.

Ligation of the cell surface receptor, CD46, alters T cell polarity and response to antigen presentation

Lymphocyte function in vivo is dictated by multiple external cues, but the integration of different signals is not well understood. Here, we show that competition for the axis of polarization dictates functional outcomes. We investigated the effect of ligation of the immunoregulatory cell surface receptor, CD46, on lymphocyte polarity during antigen presentation and cytotoxic effector function. Ligation of CD46 on human T cells prevented recruitment of the microtubule organizing center, CD3, and perforin to the interface with the antigen-presenting cell and caused a reduction in IFN-gamma production. In human NK cells, similar changes in polarity induced by CD46 ligation inhibited the recruitment of the microtubule organizing center and perforin to the interface with target cells and correlated with reduced killing. These data indicate that external signals can alter lymphocyte polarization toward antigen-presenting cells or target cells, inhibiting lymphocyte function.