1,721,048 research outputs found
Chronic rejection in vascularized composite allotransplantation
No full textPURPOSE OF REVIEW:
Vascularized composite allografts (VCA), which restore severely damaged body parts that cannot be repaired with conventional surgical techniques, often undergo acute skin rejection episodes in the early postgraft period. Although the risk of human VCA to be affected by chronic rejection was initially unknown, such cases were recently observed.
RECENT FINDINGS:
Chronic rejection targets preferentially the skin (dermal sclerosis, adnexal atrophy, necrosis) and vessels (graft vasculopathy) and may cause graft dysfunction, often resulting in ischemic graft loss. Both immune (cell-mediated and antibody-mediated) and nonimmune mechanisms seem to be involved. The early diagnosis and management of chronic rejection are challenging. Changes of chronic rejection may be seen macroscopically on the skin and can be confirmed with skin and deep tissue biopsies. New noninvasive imaging techniques, which allow visualization of the allograft vasculature, seem promising for the noninvasive detection of graft vasculopathy.
SUMMARY:
Although some features of chronic rejection of VCA start to be known, several important questions remain to be answered, concerning namely the proper definition of chronic rejection, precise diagnostic criteria, better understanding of triggering factors and pathogenetic mechanisms involved and, most importantly, adequate treatment. Ideally, chronic rejection should be prevented in the future by efficient tolerance-inducing protocols
Immunological issues in clinical composite tissue allotransplantation: where do we stand today?
No full textComposite tissue allografts are made of histogenetically different tissues and although skin seems to be the most antigenic of them, it is unknown whether the dominant immune response is really directed against the skin or we have insufficient information on the involvement of the other components of these allografts. The first clinical signs of acute rejection manifest on the skin and microscopically the earliest lesions consist in a dermal perivascular lymphocytic infiltrate, predominantly made of CD3+/CD4+ T cells. On the basis of the histological changes, a specific score (Banff score 2007) has been established to assess the severity of rejection. Despite the high incidence of acute rejection episodes, they can be completely reversed when promptly diagnosed and treated. C4d deposits in the skin and circulating donor-specific antibodies are rarely detected, suggesting that humoral rejection does not play a significant role in composite tissue allotransplantation. Chronic rejection features are still unknown. The majority of recipients have been maintained on an immunosuppressive regimen consisting of tacrolimus, steroids, and mycophenolate mofetil. The complications in composite tissue allotransplantation are similar to those usually reported after solid organ transplantation and have prompted different strategies to minimize the maintenance immunosuppression or to induce donor-specific tolerance. Furthermore, to what extent the immunosuppression can be tapered is unknown, as well as the influence of donor bone-marrow infusion in tolerance and chronic rejection. The increasing number of patients and the longer follow-up hopefully will allow answering these questions
Fifteen years later: main lessons from composite tissue allografts.
No full textComposite tissue allografts (CTA) are also called "reconstructive transplantation" as they are a valid alternative approach to repairing complex tissue defects. These procedures are still considered "experimental" and their therapeutic value remains to be validated. An immunosuppressive treatment similar to that used in solid organ transplantation allows CTA survival and function despite a high rate of acute rejection (AR) episodes. Clinical experience seems to confirm that skin is the most antigenic tissue and the first target of AR episodes, which are easy to reverse and do not seem to adversely influence graft survival and function when promptly treated. Chronic rejection can also occur in CTA, although its features are still unclear. Upper-extremity or face-transplanted patients show a relevant sensorimotor recovery. Patients are able to perform the majority of daily activities and to lead normal social lives. Global cortical remodeling occurs in the months following transplantation, reversing the functional reorganization induced by the amputation. Appropriation of the graft occurs in parallel with functional recovery. The patients' compliance is essential for the success of CTAs as well as careful recipient selection and patient follow-up to prevent complications of long-term immunosuppression
Self-renewal capacity of human epidermal Langerhans cells: observations made on a composite tissue allograft
No full textEpidermal Langerhans cells (LC) are dendritic, antigen-presenting cells residing within mammalian epidermis and mucosal epithelia. When massively depleted, they are replaced by cells of bone-marrow origin. However, their renewal within normal skin under steady-state conditions is not precisely known. We observed that epidermal LC within a human hand allograft remain stable in the long term (10 years) and are not replaced by cells of recipient's origin; furthermore, we observed a Langerhans cell in mitosis within the epidermis 8 years postgraft. These results show that under almost physiological conditions, human LC renew in the epidermis by local mitoses of preexisting cells
Alopecia areata in a composite tissue (hand) allograft recipient following graft rejection.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Absence of c4d deposition in human composite tissue (hands and face) allograft biopsies: an immunoperoxidase study
No full textDeposition of the C4d complement degradation product has been shown to be a marker of antibody-mediated rejection of solid organ allografts, including kidney, heart, liver, and lung. We investigated whether C4d deposition also would be useful in monitoring rejection in human composite tissue allografts. A total of 60 mucocutaneous formalin-fixed, paraffin-embedded and four frozen biopsy specimens from four patients with composite tissue allografts (three hands, one face) taken during a period of 7 days to 7 years after graft were immunostained for C4d by an immunoperoxidase and an immunofluorescence technique, respectively. C4d deposition was not found in any of the specimens studied, even though several of them showed pathological signs of rejection. No human leukocyte antigen alloantibodies were detected in any of the patients during the study period. These results suggest that humoral rejection occurs rarely, if at all, in the setting of human composite tissue allografts
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