Die zunehmende Verfügbarkeit experimenteller Daten und Fortschritte in Rechenmethoden haben die Anwendung computergestützter Verfahren in den Lebenswissenschaften stark gefördert, insbesondere in der Hämatologie. Verschiedene Datentypen wie molekulare Profile, fluoreszenzaktivierte Zellsortierung (FACS), Bild- und klinische Daten bieten umfangreiche Einblicke in Krankheitsmechanismen. Die Verknüpfung dieser heterogenen Datenquellen ermöglicht ein tieferes Verständnis hämatologischer Erkrankungen. Ein zentraler Fokus dieser Arbeit liegt auf der Analyse von Zeitreihendaten, um Krankheitsverläufe zu modellieren und Therapieansätze zu verbessern. Diese Methoden ermöglichen Vorhersagen, z. B. über Rückfallwahrscheinlichkeiten bei Leukämiepatienten nach Absetzen der Medikation oder die Wirksamkeit personalisierter Behandlungen. Zeitreihenanalysen und mathematische Modelle werden genutzt, um dynamische biologische Systeme auf molekularer und zellulärer Ebene zu untersuchen. Die Dissertation behandelt zwei Hauptthemen: 1. Die Entwicklung und Anwendung neuer Methoden zur Analyse von Zeitreihendaten, illustriert durch zwei medizinische Beispiele: Chronische myeloische Leukämie (CML) und Gentherapie. In der CML-Forschung wurden Modelle entwickelt, die patientenspezifische Merkmale berücksichtigen und Unterschiede in der Wirkung von Medikamenten wie Imatinib und Dasatinib aufzeigen. Simulationen personalisierter Dosierungen demonstrieren das Potenzial für verbesserte Behandlungsergebnisse. Im Bereich der Gentherapie wurde eine neue Metrik eingeführt, die eine frühzeitige Erkennung pathologischer Entwicklungen ermöglicht. Zudem wird die Rolle der Datenqualität bei der Modellgenauigkeit beleuchtet. 2. Die Optimierung interdisziplinärer Zusammenarbeit zwischen Medizinern, Biologen und Modellierern. Hierfür wurde ein benutzerfreundliches Web-Tool entwickelt, das den Zugang zu Rechenmodellen erleichtert, deren Anwendung durch Nicht-Theoretiker unterstützt und die Integration modellbasierter Erkenntnisse in klinische Entscheidungsprozesse fördert. Methodisch kombiniert die Arbeit agentenbasierte und analytische Ansätze, die an Patientendaten angepasst wurden. Optimierungstechniken spielen eine Schlüsselrolle bei der Modellanpassung. Technologische Lösungen wie Webtechnologien werden eingesetzt, um die Verbreitung von Modellen zu erleichtern und die interdisziplinäre Zusammenarbeit zu fördern. Die Ergebnisse zeigen, dass mathematische Modelle effektive Werkzeuge zur Verbesserung der personalisierten Medizin sind. In der CML-Forschung wurden Modelle entwickelt, die Unterschiede in der Medikamentenwirkung identifizieren und die Bedeutung personalisierter Dosierungen unterstreichen. Im Bereich der Gentherapie wurde die Bedeutung der Datenqualität für die Genauigkeit von Vorhersagen hervorgehoben. Das Web-Tool dient als Plattform, um Rechenmodelle unabhängig von Implementierungsdetails zu teilen, und unterstützt deren Einbettung in den klinischen Alltag. Die Dissertation zeigt, dass interdisziplinäre Zusammenarbeit essenziell ist, um komplexe medizinische Fragestellungen zu beantworten. Gleichzeitig bestehen weiterhin Herausforderungen wie Kommunikationsbarrieren, unterschiedliche Terminologien und rechtliche Hürden. Die Arbeit liefert wertvolle Beiträge, um diese Hürden zu überwinden und die Forschung in den Lebenswissenschaften voranzutreiben. Insgesamt unterstreicht die Arbeit das Potenzial computergestützter Methoden für die Hämatologie und personalisierte Medizin. Die vorgestellten Ansätze bieten eine Grundlage für verbesserte klinische Entscheidungen und die Entwicklung präziserer Behandlungsmethoden. / The increasing availability of experimental data and advancements in computational methods have significantly enhanced the application of computer-based approaches in the life sciences, particularly in hematology. Various data types, such as molecular profiles, fluorescence-activated cell sorting (FACS), imaging, and clinical data, provide valuable insights into disease mechanisms. Integrating these heterogeneous data sources enables a deeper understanding of hematological disorders. A central focus of this work is the analysis of time-series data to model disease progression and improve therapeutic strategies. These methods allow for predictions, such as the likelihood of relapse in leukemia patients after discontinuing medication or the efficacy of personalized treatments. Time-series analyses and mathematical models are utilized to investigate dynamic biological systems at molecular and cellular levels. The dissertation addresses two main themes: 1. The development and application of novel methods for time-series data analysis, illustrated through two medical examples: chronic myeloid leukemia (CML) and gene therapy. In CML research, models were developed to account for patient-specific characteristics, highlighting differences in the effects of drugs such as imatinib and dasatinib. Simulations of personalized dosages demonstrate the potential for improved treatment outcomes. In the field of gene therapy, a new metric was introduced to enable the early detection of pathological developments. The importance of data quality for prediction accuracy is also emphasized. 2. Optimizing interdisciplinary collaboration between medical practitioners, biologists, and computational modelers. To this end, a user-friendly web tool was developed to facilitate access to computational models, support their use by non-theorists, and integrate model-based insights into clinical decision-making processes. Methodologically, the work combines agent-based and analytical approaches, which are tailored to patient data. Optimization techniques play a key role in model adaptation. Technological solutions, such as web technologies, are employed to disseminate models and enhance interdisciplinary collaboration. The results demonstrate that mathematical models are effective tools for advancing personalized medicine. In CML research, models were created to identify differences in drug effects and underscore the importance of personalized dosages. In the context of gene therapy, the significance of data quality for prediction accuracy was highlighted. The web tool serves as a platform for sharing computational models independently of implementation details and supports their integration into clinical practice. The dissertation highlights the essential role of interdisciplinary collaboration in addressing complex medical questions. However, challenges such as communication barriers, differing terminologies, and legal obstacles remain. This work provides valuable contributions to overcoming these hurdles and advancing research in the life sciences. Overall, the dissertation underscores the potential of computational methods for hematology and personalized medicine. The presented approaches lay the foundation for improved clinical decision-making and the development of more precise treatment methods.

En intégrant cette étude dans un contexte d'écologie du stress, l'objectif général de cette thèse est d'une part d'évaluer l'exposition et les effets des éléments traces métalliques (ETMs)et du parasitisme chez le mulot sylvestre (apodemus sylvaticus) et d'autre part de contribuer au développement de marqueurs d'exposition et d'effets toxiques non létaux. Au cours de trois sessions de capture, des individus ont été collectés dur 30 sites localisés autour de l'ancienne fonderie de Metaleurop (Nord-Pas-de-Calais) les concentrations en Cd et Pb ont été mesurées dans les organes cibles (foie et reins) et dans les poils des mulots. différents biomarqueurs d'effets toxiques létaux et non létaux ont également été mesurés. Le nombre important de mulots prélevé (n=886) a permis d'étudier l'influence des caractéristiques individuelles (âge et sexe) et des caractéristique paysagères sur les réponses des biomarqueurs. Les résultats indiquent que les concentrations en ETMs des animaux vivants sur les sites les plus contaminés s'avèrent significativement plus importantes que celles mesurées sur les autres sites. En outre, plus de 25% des mulots provenant des sites des plis pollués présente des concentrations supérieures aux seuils toxiques et ont donc un risque accru de développer des pathologies (œdème, cancers). Par ailleurs, cette étude révèle également que ETMs chez le mulot est influencée par les caractéristiques, individuelles (âge et sexe), par l'occupation des sols et qu'elle varie en fonction de la session de capture. De plus, les résultats montrent que les concentrations ETMs [...] et les caractéristiques paysagères modulent les prévalences de certains parasites. En effet, la richesse parasitaire augmente chez les individus les plus exposés aux ETMs. Ces concentrations influencent également les différents biomarqueurs d'effets létaux [...] et non létaux [...]évalués. Ces résultats illustrent donc l'intérêt du développement de biomarqueurs on létaux pour l'évaluation des effets toxiques des ETMs les plus élevées présentent des atteintes au niveau individuel [...] et au niveau cellulaire [...] Cependant, étant donnés les effets potentiels de parasitisme sur la santé de la faune sauvage, les liens de causalité entre la présence d' ETMs et les atteintes observées sont discutables. Ce travail de thèse souligne l'intérêt des approches multi-stress dans le cadre de l'évaluation de la santé de la faune sauvage. / By integrating this study in a stess-ecology Framework, the aim of this thesis is to assess exposure and effects of trace metals (TMs) and parasitism on wood mouse[…] and to contribute to the development of non-lethal exposure and toxicity makers […].This study also reveals that the accumulations of the TMs in wood mice is influenced by individual characteristics […] and landscape features and varies according to the trapping session. In addition, results show that the concentrations of TMs […] and landscape characteristics modulate the prevalence of some parasites. […].However, given the potential effects of parasitism on animals’ health, the causal links between the presence of TMs and observed alterations are questionable. This work emphasizes the importance of multi-stress approaches on wildlife’s health assessment.

Os efeitos protetores da imunidade humoral são medidas por uma família de glicoproteínas chamadas anticorpos ou imunoglobulinas. As preparações de imunoglobulina G (IgG) utilizadas em nosso país são importantes. No Brasil, a primeira preparação de IgG foi obtida na Fundação Pró-Sangue Hemocentro de São Paulo em 1993. O presente estudo avaliou preparações de IgG obtidas de misturas de plasma humano de variadas procedências, inclusive a preparação obtida no Brasil. Foram avaliados os seguintes parâmetros: concentração protéica, distribuição das subclasses da IgG, atividade de anticorpos específicos e segurança quanto a agentes patogênicos transmissíveis pelo sangue. Em algumas preparações, a concentração protéica de IgG e a distribuição das suas subclasses estavam fora das especificações. As preparações apresentaram atividade de anticorpos específicos contra os vírus das hepatites A e B, do herpes simples, da rubéola, citomegalovírus; contra a bactéria Streptococcus pyogenes β-hemolítico do grupo A e contra o parasita Toxoplasma gondii. A qualidade de matéria-prima utilizada em algumas das preparações de IgG não foi adequada em função de reações positivas para anticorpos contra alguns agentes infecciosos, tais como HTLV I/II, HAV, HBV, HCV e Treponema pallidum. Esse estudo também mostrou a necessidade de se implantar urgente um programa abrangente para avalição das preparações de IgG a serem consumidas pela população brasileira. / A family of glicoproteins, which are called antibodies or immunoglobulins (IgG), mediates the protective effects of humoral immunity. In Brazil, the IgG for intravenous use are imported from other countries. The first Brazilian immunoglobulin G for therapheutic use was obtained from human plasma at the Fundação Pró-Sangue Hemocentro de São Paulo. The present study was carried out to evaluate different preparations of IgG, human plasmad-derived, include the preparation from Brazil. The protein concentration, IgG subclass distribution, specific antibody activities and safety regarding the main blood transmitted infectious diseases were analyzed. In some preparations, IgG protein concentration and subclass distribution were different from their specifications. Some preparations showed specific antibody activity against the following antigens: A and B hepatitis virus, rubella, herpes simplex virus, citomegalovirus, measles virus, Streptococcus pyogenes β-hemolytic group A and Toxoplasma gondii. The presence of antibodies against antigens such as HTLV I/II, HAV, HBV, HCV and Treponema pallidum has compromissed the quality guaranty of the material-source (plasma) used in some preparations. This study has also showed that a complete and effective program for the quality evaluation of IgG preparations used in Brazil is needed and should be urgently established

Cette thèse est une enquête sur le concept de niche et quelques grands cadres théoriques qui y sont apparentés: la théorie de la niche et la théorie neutraliste en écologie, la théorie de la construction de niche en biologie évolutive, et la niche des cellules souches en écologie intra-organisme. Le premier chapitre retrace l'histoire du concept de niche et confronte la théorie de la niche à une théorie concurrente, la théorie neutraliste. Le concept de niche apparaît comme devant être un explanans de la diversité des espèces et de la structure des écosystèmes. Le deuxième chapitre confronte la théorie évolutive standard à la théorie de la construction de niche, dans laquelle un organisme peut modifier son environnement et ainsi influer sur la sélection à venir. Nous montrons comment caractériser cette confrontation en termes d'échelles temporelles des processus en jeu, ce qui nous permet d'identifier le domaine de validité véritablement propre à la théorie de la construction de niche plus explicitement qu'il ne l'a été par le passé. Le troisième chapitre développe les recherches des deux chapitres précédents dans le cadre de la modélisation d'une thérapie génique comme un processus écologique de compétition et de construction de niche par les cellules. Nous présentons une famille de modèles appliqués à différentes échelles temporelles de la dynamique cellulaire, entre lesquelles le modélisateur précautionneux ne saurait choisir sans résultats expérimentaux spécifiques. Nous concluons sur les conceptions de la relation entre un organisme et son environnement attachées aux diverses facettes du concept.

Submitted by Maria Creuza Silva (mariakreuza@yahoo.com.br) on 2015-07-13T11:08:22Z No. of bitstreams: 1 DISS MP. THIAGO GRANA PINEIRO. 2015.pdf: 1759557 bytes, checksum: 8d27ab389fc62fef3a30337bbf94aa1f (MD5) / Approved for entry into archive by Maria Creuza Silva (mariakreuza@yahoo.com.br) on 2015-07-13T11:59:28Z (GMT) No. of bitstreams: 1 DISS MP. THIAGO GRANA PINEIRO. 2015.pdf: 1759557 bytes, checksum: 8d27ab389fc62fef3a30337bbf94aa1f (MD5) / Made available in DSpace on 2015-07-13T11:59:28Z (GMT). No. of bitstreams: 1 DISS MP. THIAGO GRANA PINEIRO. 2015.pdf: 1759557 bytes, checksum: 8d27ab389fc62fef3a30337bbf94aa1f (MD5) / A Constituição Cidadã de 1988 garante a saúde como direito dos brasileiros, atribuindo às esferas públicas a obrigação de articular ações de promoção, prevenção e recuperação da saúde, admitindo assim a existência de vulnerabilidade nos grupos populacionais e tornando a garantia da segurança na produção do sangue e seus componentes um desafio permanente ao Sistema Único de Saúde. Isto exige a implantação de sistemas funcionais que minimizem a probabilidade de uma unidade infectada ser transfundida. Esse estudo descreve as características que compõem os grupos de candidatos inaptos sorológicos antes e depois da implantação de uma nova tecnologia para a detecção mais rápida e eficaz de doenças infectocontagiosas, o teste de ácido nucleico (NAT). O conhecimento obtido pelo estudo pode auxiliar na adoção de ações de prevenção e proteção à saúde da população de acordo com princípios éticos que privilegiam o bem estar dos usuários e da comunidade. Trata-se de um estudo descritivo de corte transversal de natureza quantitativa. Utilizou-se dados alimentados no sistema operacional Hemovida pelo hemocentro coordenador da Bahia e foram analisados descritivamente e apresentados em gráficos e tabelas. Durante os dois períodos estudados (antes e após o uso do teste NAT) não se evidenciou achado em janela imunológica para HIV e HCV nos 2275 testes sorológicos utilizando biologia molecular. Dos testes Elisa que positivaram para HIV e HCV 85,2% e 93,7% foram respectivamente indetectáveis pelo método de biologia molecular NAT. Os resultados desse estudo, considerando seus limites, não evidenciaram ganho na segurança transfusional após a inserção do NAT no SUS da Bahia. Também não foram evidenciadas mudanças nos perfis dos inaptos sorológicos antes e depois da introdução do teste NAT. Dentre as recomendações destaca-se a necessidade dos gestores do hemocentro intervirem no achado de alta prevalência de exames positivos para sífilis.

Os efeitos protetores da imunidade humoral são medidas por uma família de glicoproteínas chamadas anticorpos ou imunoglobulinas. As preparações de imunoglobulina G (IgG) utilizadas em nosso país são importantes. No Brasil, a primeira preparação de IgG foi obtida na Fundação Pró-Sangue Hemocentro de São Paulo em 1993. O presente estudo avaliou preparações de IgG obtidas de misturas de plasma humano de variadas procedências, inclusive a preparação obtida no Brasil. Foram avaliados os seguintes parâmetros: concentração protéica, distribuição das subclasses da IgG, atividade de anticorpos específicos e segurança quanto a agentes patogênicos transmissíveis pelo sangue. Em algumas preparações, a concentração protéica de IgG e a distribuição das suas subclasses estavam fora das especificações. As preparações apresentaram atividade de anticorpos específicos contra os vírus das hepatites A e B, do herpes simples, da rubéola, citomegalovírus; contra a bactéria Streptococcus pyogenes β-hemolítico do grupo A e contra o parasita Toxoplasma gondii. A qualidade de matéria-prima utilizada em algumas das preparações de IgG não foi adequada em função de reações positivas para anticorpos contra alguns agentes infecciosos, tais como HTLV I/II, HAV, HBV, HCV e Treponema pallidum. Esse estudo também mostrou a necessidade de se implantar urgente um programa abrangente para avalição das preparações de IgG a serem consumidas pela população brasileira. / A family of glicoproteins, which are called antibodies or immunoglobulins (IgG), mediates the protective effects of humoral immunity. In Brazil, the IgG for intravenous use are imported from other countries. The first Brazilian immunoglobulin G for therapheutic use was obtained from human plasma at the Fundação Pró-Sangue Hemocentro de São Paulo. The present study was carried out to evaluate different preparations of IgG, human plasmad-derived, include the preparation from Brazil. The protein concentration, IgG subclass distribution, specific antibody activities and safety regarding the main blood transmitted infectious diseases were analyzed. In some preparations, IgG protein concentration and subclass distribution were different from their specifications. Some preparations showed specific antibody activity against the following antigens: A and B hepatitis virus, rubella, herpes simplex virus, citomegalovirus, measles virus, Streptococcus pyogenes β-hemolytic group A and Toxoplasma gondii. The presence of antibodies against antigens such as HTLV I/II, HAV, HBV, HCV and Treponema pallidum has compromissed the quality guaranty of the material-source (plasma) used in some preparations. This study has also showed that a complete and effective program for the quality evaluation of IgG preparations used in Brazil is needed and should be urgently established

No description available.

Bakgrund - Hemofili A och B är X-kromosombundna blödarsjukdomar, som beror på genetiska avvikelser i de gener som kodar för koagulationsfaktor VIII respektive IX. I dagsläget förlitar sig hemofilipatienter på kontinuerliga intravenösa injektioner med faktorkoncentrat, för att förhindra att potentiellt livshotande blödningar uppstår. Genterapi med rekombinanta adeno-associerade virus (AAV) skulle kunna erbjuda ett kurativt behandlingsalternativ, genom införandet av friska arvsanlag i hepatocyter. Syfte - Syftet med den här litteraturstudien var att undersöka huruvida genterapi medierad av AAV-vektorer är en effektiv och säker behandling mot hemofili A och B ur ett långsiktigt perspektiv. Metod - Studien är genomförd som en systematisk litteraturstudie och är baserad på sex originalartiklar framsökta via databasen PubMed, med sökorden "hemophilia AND gene therapy". Specificerade sökkriterier användes för att underlätta relevansbedömning och valet av artiklar. Resultat - En ökad endogen koagulationsfaktorproduktion kunde påvisas hos majoriteten av studiedeltagarna efter genterapibehandlingarna. Sammantaget observerades också en väsentlig blödningsreducering och en minskad faktorkoncentratanvändning. Störst förbättring noterades i de kohorter som erhållit högre genterapidoser eller den muterade faktor IX Padua-genen. Ingen immunrespons mot transgenprodukten detekterades i någon studie. Däremot sågs ett humoralt immunsvar mot AAV-kapsiden hos samtliga studiedeltagare. En mycket stor variation i T-cellssvar mot AAV-kapsiden kunde noteras. Förhöjda nivåer av alaninaminotransferas (ALAT) var den vanligast förekommande incidenten, men samtliga fall kunde framgångsrikt behandlas med glukokortikoidpreparat. Slutsats - Genterapibehandling med rekombinanta AAV-vektorer mot hemofili A och B förefaller effektiv och säker. Förhöjda ALAT-nivåer återstår dock som en behandlingsproblematik. Längre uppföljningar av fler genterapibehandlade hemofilipatienter krävs, för att kunna dra några definitiva slutsatser, väga risker mot nytta, samt optimera och individanpassa doser. / Background - Hemophilia A and B are X-linked bleeding disorders, resulting from defects in the genes encoding coagulation factors VIII and IX respectively. The current treatment for hemophiliacs entails frequent intravenous injections of coagulation factor concentrates, to prevent potentially life-threatening hemorrhages. Gene therapy utilizing recombinant adeno-associated viruses (AAV) could offer a potentially curative treatment option through the introduction of healthy genes into hepatocytes. Aim - The aim of this literature study was to investigate the long-term efficacy and safety of AAV vector-mediated gene therapy for the treatment of hemophilia A and B. Methods - The study is conducted as a systematic literature study and is based on six original articles retrieved from the search engine PubMed, using the key words "hemophilia AND gene therapy". Specific search criteria were used to facilitate the relevance assessment and selection of articles. Results - An increased endogenous coagulation factor synthesis was noted in the majority of the study participants after the gene therapy. Overall, a significant reduction in bleeding episodes and the use of factor concentrates were observed. The greatest improvements were noted in the cohorts that received the higher gene therapy doses or the mutated factor IX Padua gene. None of the study participants had an immunologic response to the transgene product. A humoral immune response against the AAV capsid was seen in all participants though. Large differences in AAV capsid-specific T-cell activation were observed. The most common adverse event was an elevation in the alanine aminotransferase (ALT) level. However, these events could be controlled with glucocorticoids. Conclusions - AAV vector-mediated gene therapy for the treatment of hemophilia A and B had a positive efficacy and safety profile. Although increased ALT levels remain a concern. Monitoring of larger numbers of study participants for longer follow-up periods is necessary for any definite conclusions to be drawn, to weigh risks against benefits and to optimize individual dosing.

Indiana University-Purdue University Indianapolis (IUPUI) / Hematopoietic stem cell (HSC) transplantation is a lifesaving therapy for a number of hematological disorders. However, to be effective, transplanted HSCs must efficiently “home” to supportive niches within the bone marrow. Limited HSC number and poor function are complications of transplant in some circumstances, and can lead to delayed engraftment and immune reconstitution, or in some cases, bone marrow failure. Enhancing HSC homing is a strategy to improve stem cell transplantation efficiency. We have previously shown that ex vivo treatment of mouse or human HSCs with 16-16 dimethyl PGE2 (dmPGE2) increases their bone marrow homing efficiency and engraftment, resulting in part from upregulation of surface CXCR4 expression. We now show that pulse-treatment of mouse or human HSPCs with dmPGE2 stabilizes HIF1α in HSPCs, and that similar treatment with the hypoxia mimetic DMOG produces analogous effects to dmPGE2 on HSPC CXCR4 expression and homing. This suggests that HIF1α is responsible for PGE2’s enhancing effects on HSPCs. Pharmacological inhibition of HIF1α stabilization in vitro with Sodium Nitroprusside (SNP), confirms the requirement of HIF1α for dmPGE2-enhanced migration and CXCR4 upregulation. Additionally, we confirm the requirement for HIF1α in dmPGE2-enhanced in vivo homing using a conditional knockout mouse model of HIF1α gene deletion. Finally, we validate that the hypoxia response element located 1.3kb from the transcriptional start site within the CXCR4 promoter is required for enhanced CXCR4 expression after PGE2 treatment. Interestingly, we also observe an increase in the small GTPase Rac1 after dmPGE2 treatment, as well as a defect in PGE2-enhanced migration and CXCR4 expression in Rac1 knockout HSPCs. Using state-of-the-art imaging technology we, confirm an increase in Rac1 and CXCR4 colocalization after dmPGE2 treatment that likely explains enhanced sensitivity of PGE2-treated HSPCs to SDF-1. Taken together, these results define a precise mechanism through which ex vivo pulse treatment of HSPC with dmPGE2 enhances HSPC function through alterations in cell motility and homing, and describe a role for hypoxia and HIF1α in enhancement of hematopoietic transplantation.

Indiana University-Purdue University Indianapolis (IUPUI) / Solid organ transplantation is limited by available donor allografts. Pig to human transplantation, xenotransplantation, could potentially solve this problem if physiologic and immunologic incompatibilities are overcome. Genetic modifications of pigs have proven valuable in the study of xenotransplantation by improving pig to human compatibility. More genetic targets must be identified for clinical success. First, this study examines platelet homeostasis incompatibilities leading to acute thrombocytopenia in liver xenotransplantation. Mechanisms for xenogeneic thrombocytopenia were evaluated using liver macrophages, Kupffer cells, leading to identification of CD18, beta-2 integrin, as a potential target for modification. When disruption of CD18 was accomplished, human platelet binding and clearance by pig Kupffer cells was inhibited. Further, human and pig platelet surface carbohydrates were examined demonstrating significant differences in carbohydrates known to be involved with platelet homeostasis. Carbohydrate recognition domains of receptors responsible for platelet clearance Macrophage antigen complex-1 (CD11b/CD18) and Asialoglycoprotein receptor 1 in pigs were found to be different from those in humans, further supporting the involvement of platelet surface carbohydrate differences in xenogeneic thrombocytopenia. Second, immunologic incompatibilities due to antibody recognition of antigens resulting in antibody-mediated rejection were studied. Identification of relevant targets was systematically approached through evaluation of a known xenoantigenic protein fibronectin from genetically modified pigs. N-Glycolylneuraminic acid, a sialic acid not found in humans, was expressed on pig fibronectin and was identified as an antigenic epitope recognized by human IgG. These studies have provided further insight into xenogeneic thrombocytopenia and antibody-mediated rejection, and have identified potential targets to improve pig to human transplant compatibility.