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Objective: Clinical diagnosis of anaphylaxis is principally based on symptoms and signs. However, particularly for patients with atypical symptoms, laboratory confirmation of anaphylaxis would be useful. This study investigated the utility of mast cell tryptase, an available clinical biomarker, for differentiating anaphylaxis from other causes of critical illness, which can also involve mast cell activation. Methods: Tryptase was measured (ImmunoCAP) in serum from patients with anaphylaxis and nonanaphylactic critical illness (controls) at ED arrival, and after 1-2, 3-4 and 12-24 h. Differences in both peak and delta (difference between highest and lowest) tryptase concentrations between groups were investigated using linear regression models, and diagnostic ability was analysed using Receiver Operating Characteristic curve analysis. Results: Peak tryptase was fourfold (95% CI: 2.9, 5.5) higher in anaphylaxis patients (n = 67) than controls (n = 120) (P < 0.001). Delta-tryptase was 5.1-fold (95% CI: 2.9, 8.9) higher in anaphylaxis than controls (P < 0.001). Optimal test characteristics (sensitivity: 72% [95% CI: 59, 82] and specificity: 72% [95% CI: 63, 80]) were observed when peak tryptase concentrations were >11.4 ng/mL and/or delta-tryptase ≥2.0 ng/mL. For hypotensive patients, peak tryptase >11.4 ng/mL had improved test characteristics (sensitivity: 85% [95% CI: 65, 96] and specificity: 92% [95% CI: 85, 97]); the use of delta-tryptase reduced test specificity. Conclusion: While peak and delta tryptase concentrations were higher in anaphylaxis than other forms of critical illness, the test lacks sufficient sensitivity and specificity. Therefore, mast cell tryptase values alone cannot be used to establish the diagnosis of anaphylaxis in the ED. In particular, tryptase has limited utility for differentiating anaphylactic from non-anaphylactic shock. [ABSTRACT FROM AUTHOR]

Apoptotic phenomena observed in vitro following isolation and following transplantation contribute significantly to islet graft loss. Strategies to reduce apoptosis of islet tissue prior to and posttransplantation may improve graft survival and function and reduce the amount of tissue necessary to achieve insulin independence. The expression of cytoprotective proteins is one such strategy that may prolong islet survival. In this light, heme-oxygenase 1 (HO-1) upregulation has been studied in both allo- and xenotransplantation models. In this study, the effect of HO-1 on apoptosis in neonatal porcine islet-like cell clusters (NPICC) was assessed. In in vitro assessments of NPICC apoptosis, NPICC showed a high sensitivity to apoptotic stimulation using a combination of TNF-alpha and cycloheximide. Stimulation with TNF-alpha alone was sufficient to induce reproducible apoptotic responses as demonstrated by caspase-3,-7 activation and subdiploid DNA analysis. Dose-dependent, high-level HO-1 protein expression was achieved following culture of NPICC in medium containing either cobalt protoporphyrin (CoPP) or cobalt mesoporphyrin (CoMP). CoPP treatment resulted in the reduction of caspase-3,-7 enzyme activity following TNF-alpha stimulation. However, such an effect was not associated with a reduction in the levels of cell death. Indeed, the inhibition of caspase enzyme activity resulted in decreased PARP-1 cleavage, which may lead to heightened levels of necrosis in treated NPICC cultures, possibly explaining the observed commitment of NPICC to the death pathway.

Research efforts have shed light on the immunological obstacles to long-term survival of pig organs transplanted into primates and allowed the identification of targets for specific immune intervention. Accordingly, the development of genetically engineered animals has overcome the hyperacute rejection barrier, with acute humoral xenograft rejection (AHXR) currently remaining the most important immunological obstacle. At this stage, a better control of the elicited anti-pig humoral immune response and avoidance of coagulation disorders are the two primary research fronts being pursued in order to overcome AHXR. Nonetheless, it is encouraging that porcine xenografts can sustain the life of non-human primates for several months. Proactive research aimed at the development of a safer organ source is also underway. It is anticipated that ongoing research in several fields, including accommodation, tolerance, immune suppression and genetic engineering, will result in further improvements in non-human primate survival. However, until convincing efficacy data and a more favourable risk/benefit ratio can be established in relevant animal models, progression to the clinic should not be viewed as an option.

Antibody-mediated mechanisms are central to the rejection that occurs when pig organs are transplanted into primates. In this article, the histopathological features of the humoral rejection process in these species combinations, namely hyperacute rejection and acute humoral xenograft rejection, will be illustrated. The profile of the natural and elicited antibodies involved will also be discussed. It has now been demonstrated that the natural immune response to a porcine xenograft is primarily directed to Galalpha1-3Gal (alphaGal) specificities, whilst the elicited immune response is directed to both alphaGal and non-alphaGal antigens. The principal characteristics of anti-alphaGal, anti-non-alphaGal and polyreactive antibodies will be described, together with the identification of the molecules recognised by natural and elicited xenoreactive antibodies. The role of the humoral immune response in the rejection of porcine islets in the primate is still uncertain and the current views on the subject will be discussed. Finally, a concise but comprehensive review of the different strategies that have been attempted to prevent the onset of antibody-mediated rejection is presented. These strategies encompass approaches aimed at interfering with the binding of xenoreactive antibodies with their targets, the use of conventional or novel immunosuppressants and splenectomy. It is undeniable that significant progress has been recently achieved in understanding the humoral rejection process of pig organs transplanted into primates. It is expected that a more comprehensive elucidation of the mechanisms underlying accommodation and tolerance may, in the not too distant future, further extend survival of pig organs transplanted into primates.