Biomedical Sciences and Technology: Peer-Reviewed Resources Other Than Journal Articles

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12521/724

Paper Presentations, Poster Presentations, Continuing Education Courses, Etc.

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Now showing 1 - 20 of 26

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Antimicrobial Properties of Thyme Essential Oil on Salmonella Typhimurium
(FASEB Journal, 2021) Santos, Anael A. Jr
Antimicrobial properties of thyme essential oil solutions (EO) oil have been identified against foodborne bacteria, but the effectiveness has not yet been fully determined. The objective of this study is to analyze the effect of thyme essential oil under standardized conditions on Salmonella Typhimurium. The Salmonella Typhimurium (ATCC 53648™) inoculum was prepared by growing the bacteria in tryptic soy broth for 24 hours at 37°C, yielding 6.9 x10 CFU/ml. One hundred microliters of the starting bacterial culture were spread onto Mueller Hinton agar plates and left to dry for 15 minutes. Treatments were formed by creating Thyme essential oil solutions (EO) of 0, 2.5, 10, 25% using 70% ethyl alcohol as the diluent. Each EO was vortexed and filtered using a 0.2 microliter sterile syringe filter. Twenty microliters of each EO were pipetted into a sterile paper disc (weight ranged of 0.0086-0.009 g). Three paper discs of each treatment containing the EO were placed on standardized locations on each inoculated plate. Each treatment consisted of 9 inoculated plates. The plates were then incubated at 37C for 24 hours. Additionally, three manufactured standard antibiotic paper discs of 5 mcg Ciprofloxacin, 10 mcg Ampicillin, and 10 mcg Streptomycin were placed on separate plates as controls. The zone of inhibition created was measured using an image processing program, Image J. All data were analyzed using the general linear model procedure for analysis of variance (ANOVA). The antimicrobial property of the EO observed as the zone of inhibition increased as the concentration of the EO increased (R= 0.91, P < 0.0001). EO at 25% showed the greatest antimicrobial effect against Salmonella Typhimurium compared to 10, 2.5, and 0% (21.5, 14.8, 10.5, and 0.0 mm, respectively; P < 0.0001). There was no significant difference (P=0.20) between the zone of inhibition of 25% E0 and ampicillin. All antibiotics had some effect against Salmonella Typhimurium where ciprofloxacin had the greatest effect; its effect was even greater than the 25% EO (29.5 vs. 21.5 mm; P< 0.0001). The 25% and 10% EO was more effective against Salmonella than Streptomycin (21.5, 14.5 vs. 12.7 mm respectively; P< 0.0001). However, the 2.5% EO was not as effective as Streptomycin (10.5 vs. 12.7 mm; P< 0.0001). In conclusion, thyme EO showed increasing antimicrobial properties against Salmonella Typhimurium as the concentration of oil increased. It proved to be more effective than streptomycin antibiotic control at concentration as low as 10% EO. Further evaluation of the effects of thyme EO is needed to determine the extent of its effectiveness against additional commensal and pathogenic organisms.
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Exploring the Descriptive-epidemiological Spatial Relationships between Social Determinants of Health and Other Factors in Relationship to Adult Asthma Burden across the United States
(Harvard Medical School, 2024-03-23) Nguyen, Tho; Gillen, Craig; Campbell, Christopher; Butler, J. Russell
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Chronic Pain “Hotspots” in a Primary Service Area: Connecting: Population Health to Clinician Experience
(Florida Academy of Sciences, 2024-03-08) Gillen, Craig; Butler, J. Russell
Chronic pain (CP, pain lasting more than three months) is a biopsychosocial condition that affects approximately 20% of the global population or ~50 million US adults. Certified nurse anesthetists observed clinical CP prevalence indicating local distribution bias. To assess this, a collaboration was formed between these clinicians and population-health researchers specializing in spatio-temporal health analytics. The goal of this study was to conduct a novel CP analysis at clinically relevant spatial scales and through a unique collaboration of clinicians and population health analysts. Most often, CP population studies are conducted at state or national levels. Our methods focus on a more appropriate clinician frame-of-reference, a primary service area (PSA) of a healthcare institution. We created a healthcare facility’s 30-minute drive time in which we geo-attached race/ethnicity and socio-economic variables to all 232 census tracts (CT). Then using an established source (Centers for Disease Control) CP calculations per race/ethnicity, economic variables, and age class, we calculated CP prevalence per CT and PSA. We conducted statistical “hotspot” analyses. We found that CP could be affecting 132,000 people in the PSA and that it differentially affects minorities and people of lower incomes. The hotspot results indicated that they accounted for 32% of the population, but ~ 40% of low income and 47% of Black PSA, CP prevalence. The “coldspots,” 11% of population accounted for 7% & 5% of PSA low income and Black CP, respectively. These types of collaborations and analyses will better inform clinicians and health professionals as the industry begins to shift away from fee-for-service and to value-based and capitation reimbursement models.
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Descriptive Spatial Analysis of Chronic Disease Distributions in U.S. Census Tracts
(Harvard Medical School, 2023-04-02) Campbell, Christopher; Gillen, Craig; Butler, J. Russell
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Using Micro-GIS to Analyze and Quantify the Functional Topology of Tuberculosis Granuloma
(Florida Academy of Sciences, 2023-03-10) Gillen, Craig; Butler, J. Russell
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The Role of Micro-GIS in Spatial Biology
(Stanford University, 2023-08-29) Butler, J. Russell
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Spatial Analysis of Immuno-metabolism Across Non-human Primate Granuloma Tissue Preparations
(University of Michigan, 2024-02) Butler, J. Russell
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Purpura Fulminans Triggered by the Formation of Anti-endothelial Autoantibodies in a Patient with Chronic Lymphocytic Leukemia
(Society of Thrombosis and Haemostasis Research, 2022-03) Amirkhosravi, Ali
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What We Have Lost: Recovering our Hippie Roots and the Depth of Environmental Education
(League of Environmental Educators in Florida, 2024-03) Scarbrough, John R.
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Combating Environmental Exceptionalism: Integrating Ecological Literacy and Appreciation of Nature into Educational Curricula
(League of Environmental Educators in Florida, 2021) Scarbrough, John R.
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The role of Human Fc Gamma Receptors in the Pathophysiology of Lupus Syndrome
(FASEB Journal, 2019) Amirkhosravi, Ali; Santos, Anael A. Jr
Systemic Lupus Erythematosus (SLE) is a chronic autoimmune syndrome, which currently has no curative treatment. The main drivers of this inflammatory disease are the IgG family autoantibodies that are produced against self-antigens resulting from dysregulated apoptosis. These pathogenic autoantibodies form immune complexes (ICs), which become deposited in various tissues and cause organ damage. IgG ICs mainly interact with target cells by engaging with a family of receptors known as Fc gamma receptors (FcγRs). FcγRs are thought to be important contributors to inflammation in autoimmune diseases such as SLE. These receptors cooperate in modulating antigen processing and presentation, autoantibody production, and the promotion of inflammatory processes. Current mouse models do not adequately produce translatable data regarding the crucial role of FcγRs in SLE pathogenesis because the repertoire of FcγRs in mice is significantly different to that of humans. The human FcγR family consists of FcγRI, FcγRIIa, FcγRIIb, FcγRIIIa, and FcγRIIIb whereas mice express FcγRI, FcγRIIb, FcγRIII and FcγRIV. Furthermore, FcγRIIa, which is absent in wild type (WT) mice, is the only IgG receptor present on human platelets. The present study used the pristane method of lupus induction in WT mice and in mice in which all murine FcγRs have been replaced by human FcγRs (hu-FcγR mice) to study the role of individual human FcγRs in the initiation and progression of lupus-like autoimmune syndrome. After chemically inducing SLE in hu-FcγR mice, we have found that both the initiation and progression of SLE is significantly accelerated compared to WT mice, suggesting that the combination of human FcγRs play a dominant role in the pathogenesis of lupus. Symptoms such as hypothermia, chopped breathing and weight loss was present in 61% of hu-FcγR mice after 15 days or less after injection compared to only 33% in WT mice (p<0.05). hu-FcγR mice presented splenomegaly, glomerulonephritis, and lung vasculitis as early as 10 days after injection. Antinuclear antibodies were found in 47% of injected hu-FcγR mice compared to 28% in WT mice (p<0.05). These results suggest that FcγRs can significantly affect the development of a lupus-like syndrome in mice. Furthermore, mice with human FcγRs should be considered as a more suitable model to study autoimmune disorders such as SLE. The present study and other necessary investigations in this topic may not only profoundly impact our knowledge of inflammation in SLE, but also identify specific FcγRs as novel therapeutic targets. Ultimately, because of the involvement of FcγRs in modulation of the inflammatory response, our findings have the potential to impact therapeutic approaches for other inflammatory autoimmune disorders, such as rheumatoid arthritis and antiphospholipid syndrome.
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CD32 Antibodies Protect FCGR2A Mice from IGG-mediated Hypersensitivity Reactions and Thrombosis
(Journal of Thrombosis and Haemostasis, 2015) Amirkhosravi, Ali
Background: CD32a activation by IgG immune complexes (IC) mediates thrombosis and shock in CD32A transgenic (Tg) mice. FCGR2A mice carry the CD32A transgene and are immune-competent, whereas endogenous IgG receptor (FcgR) knockout mice crossed with CD32A Tg mice are selectively immunodeficient. Hypersensitivity Reactions (HR) to IgG are mediated by FcgRs such as CD32a and are Type II (HR-T2; cell-bound IgG) or Type III (HR-T3; IgG IC). Certain IgGs induce in CD32A mice either HR-T2 reactions and thrombocytopenia without thrombosis, or HR-T3 reactions with concomitant thrombosis. CD32a monoclonal antibody (mAb) blockade, such as by IV.3, could prevent such reactions, but induces anaphylaxis in immunodeficient CD32A Tg mice, suggesting mAb CD32a targeting is not feasible. Aims: (1) to determine whether immune-competent CD32A Tg mice react to CD32a mAbs as do immunodeficient CD32A Tg mice and whether such reactions mechanistically are HR-T2 or T3; (2) to test the effect of CD32a blockade by mAbs on IgG IC-induced thrombotic shock. Methods: Various CD32a mAbs were injected into FCGR2A mice. Mice were challenged with IgGs that induce thrombocytopenia with or without thrombotic shock. Platelets were counted before and after CD32a mAb injection or exposure to active IgGs. Animals were observed for hypothermia and shock symptoms. Lung thrombosis was assessed histologically. Results: CD32a mAbs induced thrombocytopenia independently of and concomitantly with HR-T2 (but not T3) reactions without thrombosis in FCGR2A mice. Such reactions were not observed with corresponding aglycosyl CD32a mAbs, which also completely prevented IgG IC-induced thrombosis. Conclusion: IgG-induced thrombocytopenic, thrombotic, and hypersensitivity reactions can be differentiated in FCGR2A mice. CD32 mAbs cause HR-T2 without thrombosis which is avoided by deglycosylation. Whole aglycosyl CD32a mAbs can thus be safely infused into CD32A Tg mice and completely prevent HR-T2 and T3, and thrombosis.
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Converging Roles of Platelets and CD32a in IGG-mediated Hypersensitivity Reactions
(Journal of Thrombosis and Haemostasis, 2015) Amirkhosravi, Ali
Background: Injection of certain IgGs into CD32A transgenic mice causes hypersensitivity reactions (HR), which are thought to be largely neutrophil-driven. The presence of CD32a on platelets in these mice fundamentally alters the nature of HR by introducing complexities involving thrombosis and spleen function. Aims: We set out to identify differential responses to anti-platelet antibodies vs. immune complexes in CD32A mice and to identify the impact of platelet depletion and splenectomy on IgG-mediated HR. Methods: HR and thrombosis were evaluated following injection of monoclonal (mAb) or polyclonal (pAb) antibodies directed against platelet or soluble antigens, including: (1) IV.3 (mAb that binds platelet CD32a), and rabbit anti-mouse-platelet pAbs; (2) thrombotic IgG immune complexes (IC) consisting of CD40L+anti-CD40L mAb or b2GPI+anti-b2GPI pAb. These were injected into mice having or lacking CD32a, in some cases following platelet depletion or splenectomy. Reactions to these IgGs were assessed by signs of HR and by measurement of core body temperature, platelet counts, and pulmonary thrombosis. Results: IV.3 caused HR but not thrombosis in CD32A mice which was markedly suppressed by platelet depletion, suggesting platelets are primary mediators of IV.3-induced HR in this model. IV.3 caused HR similarly in control or splenectomized CD32A mice, suggesting splenic involvement is not required. Rabbit anti-mouse platelet pAbs caused HR in CD32A but not WT mice, suggesting a requirement for CD32A. Finally, platelet depletion significantly blunted both IC-induced HR and thrombosis. Conclusion: These data indicate that platelets per se, and in particular platelet CD32a, play primary roles in IgG-mediated hypersensitivity reactions in CD32A transgenic mice. They also highlight the importance of including platelets in the analysis of hypersensitivity reactions in mouse models, underscoring the value of CD32a in translating mouse model results to human pathology.
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Clinical Significance of Circulation Tissue Factor (TF) in Women with Suspected Ovarian Cancer
(Journal of Thrombosis and Haemostasis, 2015) Amirkhosravi, Ali
Background: The interplay between malignancy, inflammation, and coagulation is well established. It is currently unclear, however, whether preoperative assessment of circulating TF provides valuable additional information in women presenting with ovarian masses of unknown etiology. Aims: To evaluate circulating TF as a diagnostic tool in suspected ovarian cancer. Methods: In a prospective single-center cohort study, we measured preoperative plasma levels of D-dimer, TF antigen, microparticle-associated TF-specific procoagulant activity (MP TF PCA), and soluble P-selectin (sCD62P) in 40 women with a final diagnosis of ovarian cancer in comparison to 15 women with benign tumors, all of whom underwent exploratory surgery, and 34 healthy females. Results: D-Dimer, MP TF PCA, and sCD62P, but not TF antigen and CA125, were significantly increased in cancer patients, while levels of hemostatic markers were similar in patients with benign tumors and healthy controls. Plasma depletion of MPs did not significantly alter TF antigen levels, as measured by ELISA, suggesting that this assay predominantly captured a soluble TF variant. In cancer patients, only D-Dimer and CA125 correlated with the FIGO stage. Abnormal levels of D-dimer had the highest sensitivity (93%), while increased MP TF PCA had the highest specificity (78%) for the diagnosis of cancer. Perioperative venous thromboembolism (VTE) occurred in 16% of cancer patients and was associated with an advanced FIGO stage, while sCD62P and plasma fibrinogen, an acute-phase reactant, were correlated with the Khorana score, a validated VTE risk assessment tool in ambulatory cancer patients. Conclusion: While D-dimer, by reflecting the overall impact of the cancer on the hemostatic system, is correlated with tumor burden, shedding of MP TF PCA may provide complementary information relevant to malignant transformation and cancer biology. In this regard, technically demanding analysis of MP TF PCA cannot be replaced by measurement of plasma TF antigen.
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Identification of Protein C system-associated Thrombophilia Using an Endothelial Cell-based Thrombin Generation Assay
(Research and Practice in Thrombosis and Haemostasis, 2018-07) Amirkhosravi, Ali
Background: Defects in the Protein C (PC) system are associated with an increased risk of venous thrombosis, due to a failure to regulate thrombin production. The thrombin generation assay (TGA) may therefore be a useful tool to demonstrate the potential hypercoagulable phenotype of patients with such conditions. We previously showed that the introduction of a surrogate endothelial monolayer to the TGA allows the assessment of the endothelial-dependent PC pathway. Thus, by measuring thrombin generation (TG) kinetics ± these cells, the contribution of the PC anticoagulant system to TG can be assessed in a physiologically relevant manner. PC- or S-depleted (PCd, PSd), as well as factor V Leiden (FVL) plasmas all show an abnormal TG profile in this endothelial-based TG assay (EcTGA). Aims: We investigated whether the EcTGA was capable of detecting a TG abnormality in clinical samples having PC/PS deficiency or FVL. Methods: Residual plasma samples of 151 in-hospital patients tested for thrombophilic abnormalities in our Hemostasis and Thrombosis Clinical Lab were subjected to EcTGA. Results were expressed as % reduction in TG in the presence of endothelial cells. Normal (n=69), FVL, and PCd/PSd plasmas served as abnormal controls. Results: The use of therapeutic anticoagulation prior to sample collection precluded the acquisition of meaningful thrombograms in 125 samples. Of the remaining 26, 18 (69%) had a PC system-related defect. However, other hemostatic abnormalities (commonly an elevated FVIII) were also present, and only 4 (15%) had a unique defect. Abnormal TG profile was observed in 11 of 18 (61%) patients based on a % reduction of TG parameters (PT & ETP) falling below the 10th percentile cut-off derived from normals. Conclusions: EcTGA may be a useful global assay to screen for the presence of PC system-associated thrombophilic abnormalities. However, the frequency of anticoagulation and the “acute-phase” status of hospitalized patients could preclude analysis or affect assay sensitivity in this population.
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Blockade of the Neonatal Fc Receptor (FcRn) Represents an Effective Mechanism for the Removal of Pathogenic Autoantibodies in Primary Immune Thrombocytopenia
(Blood, 2017) Amirkhosravi, Ali
Introduction: The neonatal Fc receptor, FcRn is ubiquitously expressed, & is responsible for maintaining the half-life of IgG & albumin, by rescuing these proteins from intracellular lysosomal degradation. Blockade of the interaction of FcRn with IgG would be expected to prevent salvage of both non-pathogenic and pathogenic IgG. Patients with primary immune thrombocytopenia (ITP) have autoantibodies against platelet membrane proteins such as the cell adhesion receptor CD61/CD41 (GPIIb/IIIa). Rozanolixizumab (a high affinity IgG4 monoclonal antibody (mAb) that specifically inhibits IgG binding to FcRn) is currently being evaluated in phase 2 clinical studies in patients with ITP. The aim of the current study was to understand the in vitro properties of rozanolixizumab & to explore the in vivo effects of a surrogate anti-mouse FcRn mAb (murinized “4464”) in a mouse model of ITP. Methods: The affinity of rozanolixizumab for FcRn was tested using surface plasmon resonance technology (Biacore), with the antibody captured by an anti-Fc immobilized on the sensor chip & soluble FcRn in solution, whilst the affinity of fluorescently labelled rozanolixizumab for human FcRn expressed on the surface of Madin-Darby canine kidney (MDCK) cells was measured by flow cytometry. Recycling & transcytosis of human IgG (hIgG) was also assessed in FcRn-transfected MDCK cells. For IgG tracking experiments, endothelial & epithelial cell lines were incubated with an AF647-conjugated IgG for 24 hours in the presence or absence of rozanolixizumab. Prior to imaging, nuclei were labelled using Hoechst at 37°C & cells were then visualized by fluorescence microscopy. Phagocytosis of anti-human MHC I (W6/32)-coated platelets by THP-1 cells was assessed by flow cytometry at 1 hour. The effect of rozanolixizumab on IgG recycling in vivo was assessed in the human FcRn-transgenic (hFcRn-Tg) mouse: hIgG at 500mg/kg was administered IV to mice on day 1 & dosed with antibodies on day 2; serial bleeds were then taken at multiple time points post antibody dosing & levels of hIgG, albumin & rozanolixizumab were quantified using LC-MS/MS. For the induction of ITP in mice, animals received an anti-CD41 antibody (MWReg30), delivered by osmotic minipump (~1µg of antibody delivered every 24 hours) & the anti-mouse FcRn mAb (4464) was administered at 30mg/kg either on days 0, 2 & 4 (prophylactic dosing) or on days 3 & 5 (therapeutic dosing); IVIg (1g/kg) was also evaluated & control mice received either PBS or an isotype-matched control mAb (101.4). Daily blood samples were taken to assess platelet numbers. Results: Rozanolixizumab has a high affinity for FcRn in a protein-protein (Biacore) assay with a KD of ~25pM at both pH6.0 & pH7.4; in the cell-based assay, the affinity was 1nM at both pH's. Rozanolixizumab efficiently inhibited the recycling & transcytosis of IgG in human FcRn-transfected MDCK cells (IC50 0.4nM & 1.1nM, respectively). Confocal microscopy experiments showed that there was an increased accumulation of IgG in cells in the presence of rozanolixizumab, relative to an isotype control mAb, & that the IgG was co-localized in lysosomes where it appeared to be degraded. FcRn has been postulated to play a direct role in phagocytosis, but the phagocytosis of opsonized platelets by THP-1 cells was unaffected by blockade with rozanolixizumab. Treatment with rozanolixizumab resulted in a dose-dependent accelerated clearance of hIgG in the hFcRn-Tg mouse; hIgG levels in all treated groups were significantly lower vs PBS controls from 24 hours post-dosing until the end of the experiment 8 days post dosing (p<0.01). No effect on albumin levels occurred in these mice. In the mouse model of ITP, both prophylactic & therapeutic treatment regimens with 4464 resulted in an increased number of platelets compared to control animals that received either PBS or 101.4. Animals that received 4464 from day 0 had significantly greater platelet numbers than control animals on days 4 & 5 (p<0.05); therapeutic dosing gave a significantly greater platelet number than control animals on day 5 (p<0.05). Conclusion: Rozanolixizumab is a high affinity mAb that inhibits the IgG recycling function of FcRn in vitro & in vivo . An anti-mouse FcRn mAb demonstrated efficacy in a mouse model of ITP. These data support the evaluation of rozanolixizumab in patients with ITP, & a phase 2 clinical study is currently ongoing in this patient population.
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A Novel Role for the Membrane Protein G6f in Platelet Activation Induced by Weak Stimulation
(Research and Practice in Thrombosis and Haemostasis, 2017-07) Amirkhosravi, Ali
Background: The lymphocyte antigen 6 complex locus protein (G6f) is a type I transmembrane protein of the immunoglobulin super family that is expressed on the surface of human platelets. The intracellular tail of G6f contains a single tyrosine in a single YXXI motif, which undergoes phosphorylation in response to GPVI and αIIbβ3-mediatedplatelet activation. This leads to the binding of the adaptor proteinGrb2 to G6f. G6f is currently considered to be platelet-specific, but its function remains unknown. Aims: In this study, we investigated if antibodies against this mem-brane protein can influence platelet activation and aggregation caused by various agonists. Methods: Washed platelets were stimulated with low doses of agonists: thrombin (0.03-0.05 U/ml), ADP (10 μM), IgG immune complexes (IC, 40-100 nM) and collagen related peptide (CRP, 0.25-1μg/ml) with or without anti-G6f antibodies. Platelet aggregation and dense granule release were assessed by aggregometry and the serotonin release assay, respectively. Results: Platelet aggregation and granule release induced by low dose thrombin, ADP (aggregation only) and IC were strongly inhibited(>80%) by the anti-G6f antibodies whereas CRP-induced platelet activation was inhibited by 40%. These effects were not observed with higher agonist concentrations. Conclusions: Our results suggest a novel role for G6f in platelet activation caused by a broad range of agonists. The results also indicate that anti-G6f antibody promotes an inhibitory effect against agonist-induced platelet activation and aggregation. G6f may there-fore represent a possible anti-thrombotic target. However, additional mechanistic studies are required to address this.
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Platelet Activation by Antiphospholipid Antibodies through the IgG Receptor FcγRIIa: Possible Role in Thrombosis Associated with Antiphospholipid Syndrome?
(Research and Practice in Thrombosis and Haemostasis, 2017-07) Amirkhosravi, Ali
Background: Antiphospholipid antibodies (aPLAbs) targeting beta-2glycoprotein I (B2GPI) are of primary importance in thrombosis associated with antiphospholipid syndrome (APS). The predominance of the IgG isotype in APS is conspicuously linked with increased risk of thrombosis, raising the question whether the platelet IgG receptor,FcγRIIa, may play a role in thrombosis caused by aPLAbs, as is the case in heparin-induced thrombocytopenia in which heparin Abs directly activate platelets through FcγRIIa. We have previously shown that:(1) goat anti-human B2GPI-Abs ± human B2GPI strongly activate human platelets in vitro, and that this activity is abolished by the anti-FcγRIIa antibody IV.3;(2) anti-B2GPI immune complexes are thrombotic in mice transgenic for human FcγRIIa but not in wild type mice. Aims: We sought to investigate if IgG from patients with aPLAbs can activate platelets in a manner dependent on FcγRIIa.Methods: IgG was purified from plasma of 46 patients with aPLAbs and/or lupus anticoagulant. The capacity of the IgG to activate plate-lets (±B2GPI) was evaluated by serotonin release assay (SRA) and washed platelet aggregation (WPA). With WPA, platelets ± IV.3 were either: (a) primed with ADP followed by IgG introduction or (b) incubated with IgG (30 min) followed by introduction of low thrombin concentrations. Results: With or without B2GPI, IgG from 10 of 46 (22%) patients caused platelet dense granule release. In all cases this was abolished by IV.3, indicating the dependence of FcγRIIa. Aggregation of ADP-primed platelets was observed with 1 of 2 of the above10 IgGs. Preincubation of platelets with aPL IgG from 2 patients, sensitized platelets to aggregate in response to otherwise subaggregetory thrombin stimuli. This effect was also abolished by IV.3.Conclusions: These findings suggest that aPLAbs from patients can directly activate and/or sensitize platelets in a FcγRIIa-dependent manner. This mechanism may contribute to thrombosis in patients with aPLAbs.
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Induction of ImmuneThrombocytopenia in Mice Expressing Human Fcy Receptors: An Improved Experimental Model that Better Reflects the Inflammatory State Associated with ITP
(Research and Practice in Thrombosis and Haemostasis, 2017-07) Amirkhosravi, Ali
Background: Fcγ receptors (FcγRs, e.g. FcγRIIa) contribute to the pathophysiology of immune thrombocytopenia (ITP). Mouse models are often used to study the biology of ITP. In these, thrombocytopenia is achieved by passive administration of anti-platelet antibodies. However, they fail to reflect the inflammatory state associated with human ITP. Differences in the types and ex-pression patterns of FcγRs between humans and mice may contribute to this discrepancy. Aims: Here, using mice transgenic for human FcγRs, we assessed ITP induced by native or chimeric anti-mouse platelet antibodies. Methods: Mice transgenic for either the entire human Fcγ-receptorfamily (huFcγR) or only FcγRIIa (hFc), and wild type (WT) mice, were injected i.v with anti-mouse platelet antibodies: MWReg30, 6A6 or chimeric 6A6 (c6A6), containing rat, mouse or human Fc domains, respectively. Core temperature and platelet counts were measured before and 30 min after injection. Alternatively, MWReg30 and c6A6were injected i.p and platelets counted daily for 7 days. Plasma IFN-γ,TNF-α, IL-2, IL-6 and IL-10 were measured 30 min after i.v, and on days0, 3, 5 and 7 after i.p injections. Results: MWReg30 injected i.v induced severe thrombocytopenia(>90% platelet loss), hypothermia, and shock in huFcγR and hFc but not WT mice. 6A6 caused severe thrombocytopenia in huFcγR and hFc but hypothermia and shock only in huFcγR. In contrast, c6A6caused mild thrombocytopenia (30% platelet loss) without hypothermia or shock in all strains. Severe sustained thrombocytopenia was achieved in all strains injected i.p. Significant elevation of IFN-γ, TNF-α, IL-6 and IL-10 levels was observed in huFcγR mice injected i.v or i.p. with MWReg30, and in both huFcγR and hFc mice with c6A6, but not in WT mice. Conclusions: The use of anti-platelet antibodies having a human effector region in mice expressing human FcyRs is an improved model that more closely reflects the pathophysiology of human ITP and reveals its inflammatory nature.
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Thrombo-protective Effect of Anti-FcyRIIa Monoclonal Antibodies in an Acute Mouse Model of Immune Complex-induced Thrombosis
(Thrombosis & Hemostasis Societies of North America, 2016-04) Amirkhosravi, Ali

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