Background: Rejection is considered as a major barrier to achieve successful transplantation. Non self-human leucocyte antigen (HLA) is a well-known antigenic target for antibodies binding that can result in antibody-mediated rejection (AMR). To reduce risk of rejection in kidney transplant, preventive measures are undertaken, which include HLA-matching between donor and recipient, and in-vitro pre-transplant crossmatch with potential donor cells and recipient sera, furthermore, periodic HLA antibodies monitoring for donor-specific antibodies (DSA) is carried out before and after transplant. Nevertheless, allograft may still fail despite the above measures, which suggests other antigens besides HLA can also contribute to renal rejection. In fact, polymorphic major histocompatibility complex (MHC) class I–related chain A (MICA) antigens and Angiotensin II type 1 receptor (AT1R) antigens have been reported as likely targets in AMR. However, the effect of non-HLA antibodies such as anti-MICA and anti-AT1R antibodies in rejection are not fully defined. This implies there is an imminent need to elucidate the role of non-HLA antibodies in allograft AMR cases which are not mediated by HLA antibodies. Aim: To retrospectively evaluate the occurrence of MICA and AT1R antibodies in 21 clinical AMR cases without detectable HLA antibodies or HLA antibodies that were not target against donor HLA. Methods: Twenty-one cases with suspected non-HLA mediated post-transplant rejection were retrieved. Eplet analysis was utilized to confirm that the detectable HLA-DR antibodies in one of the samples were not cross-reactive towards a donor’s antigen. Sera from 21 non-AMR cases were used as controls. All sera were subjected to MICA antibody and AT1R antibody screening. Identified positive cases were further examined with their pre-transplant sera to assess whether the AT1R and/or MICA antibodies were already pre-formed before transplantation. The sensitization histories of transfusion, pregnancy and previous transplantation were recorded. Results: Nine of twenty-one cases were detected with MICA and/or AT1R antibodies. 7 samples were detected with MICA antibodies while 3 samples were detected with AT1R antibodies. A sample was detected with both MICA and AT1R antibodies. Importantly, the presence of MICA/AT1R antibodies appeared to be strongly associated with rejection caused by non-HLA antigens (p=0.0007). All controlled cases were found to be negative for MICA and AT1R antibodies. Pre-transplant sera of the positive cases were further screened and pre-formed antibodies were detected in 3 of the positive MICA cases, and 1 of the positive AT1R cases. Since no AT1R and MICA genotyping of the donor was carried out previously, it was uncertain that the allograft rejection was induced by the donor specific pre-formed antibodies generated in the pre-transplant sensitization events. Nonetheless, AT1R and MICA antibodies appeared to be induced by the allograft in the remaining 5 cases. Conclusion: Presence of MICA/AT1R antibodies appeared to be associated with the investigated AMR cases without detectable HLA antibodies. Some evidence suggested the production of these non-HLA antibodies could be induced by transfusion sensitization or allograft upon transplantation. / published_or_final_version / Pathology / Master / Master of Medical Sciences

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 5 uppsatser.

Thesis (M.S.)--Rochester Institute of Technology, 1993. / Typescript. Includes bibliographical references (leaf 69).

No description available.

A extrusão do polietileno linear de baixa densidade (LLDPE) é limitada por um defeito de processamento conhecido como fratura do fundido, que é um defeito de superfície no polímero extrudado. Esta torna-se áspera, resultando na perda do lustro e em uma mudança de determinadas propriedades de superfície. O objetivo deste trabalho foi obter um copolímero do politetrafluoroetileno reciclado com uma olefina que possa melhorar o processo de extrusão do LLDPE. O copolímero é obtido por meio da irradiação do PTFE reciclado sob atmosfera inerte para obter os radicais livres e, posteriormente, adicionado o monômero olefínico visando a sua enxertia na matriz polimérica (PTFE). Após um tempo de contacto, faz-se um tratamento térmico para a recombinação e eliminação dos radicais, ambos sob atmosfera reativa e/ou inerte. Foram utilizados três monômeros olefínicos, acetileno, etileno e 1,3-butadieno. O monômero 1,3-butadieno mostrou-se mais efetivo na enxertia. Os resultados foram caracterizados pela espectroscopia de absorção na região do infravermelho com transformadas de Fourier (FTIR), análise termogravimétrica (TGA) e termogravimetria derivada (DTG). O copolímero obtido foi misturado nas concentrações de 0,2 a 2,0 % em massa com o LLDPE. As propriedades reológicas desta mistura foram determinadas com um reômetro de torque. Os resultados demonstram que o processo utilizado fornece um copolímero que, usado como aditivo ao LLDPE, melhora o processo de extrusão eliminando o defeito de processamento conhecido como fratura do fundido. / The extrusion of linear low density polyethylene (LLDPE) is limited by a process related defect known as ‘melt fracture’ or ‘sharkskin’, which is a surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and in alterations of specific surface properties. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by the addition of an olefinic monomer to graft the latter in the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to permit recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. Three olefinic monomers were used, namely; acetylene, ethylene and 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). 0.2-2.0 wt% of the copolymer that was obtained was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the process used rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect ‘melt fracture’.

A extrusão do polietileno linear de baixa densidade (LLDPE) é limitada por um defeito de processamento conhecido como fratura do fundido, que é um defeito de superfície no polímero extrudado. Esta torna-se áspera, resultando na perda do lustro e em uma mudança de determinadas propriedades de superfície. O objetivo deste trabalho foi obter um copolímero do politetrafluoroetileno reciclado com uma olefina que possa melhorar o processo de extrusão do LLDPE. O copolímero é obtido por meio da irradiação do PTFE reciclado sob atmosfera inerte para obter os radicais livres e, posteriormente, adicionado o monômero olefínico visando a sua enxertia na matriz polimérica (PTFE). Após um tempo de contacto, faz-se um tratamento térmico para a recombinação e eliminação dos radicais, ambos sob atmosfera reativa e/ou inerte. Foram utilizados três monômeros olefínicos, acetileno, etileno e 1,3-butadieno. O monômero 1,3-butadieno mostrou-se mais efetivo na enxertia. Os resultados foram caracterizados pela espectroscopia de absorção na região do infravermelho com transformadas de Fourier (FTIR), análise termogravimétrica (TGA) e termogravimetria derivada (DTG). O copolímero obtido foi misturado nas concentrações de 0,2 a 2,0 % em massa com o LLDPE. As propriedades reológicas desta mistura foram determinadas com um reômetro de torque. Os resultados demonstram que o processo utilizado fornece um copolímero que, usado como aditivo ao LLDPE, melhora o processo de extrusão eliminando o defeito de processamento conhecido como fratura do fundido. / The extrusion of linear low density polyethylene (LLDPE) is limited by a process related defect known as ‘melt fracture’ or ‘sharkskin’, which is a surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and in alterations of specific surface properties. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by the addition of an olefinic monomer to graft the latter in the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to permit recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. Three olefinic monomers were used, namely; acetylene, ethylene and 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). 0.2-2.0 wt% of the copolymer that was obtained was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the process used rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect ‘melt fracture’.

This thesis focuses on evaluating the osteogenic potential of two synthetic bone graft materials either in vitro and/or in established rodent bone defect models.

No description available.

No description available.