Importance of T cells to accelerated rejection and acceptance of renal allografts in sensitized rat recipients

BACKGROUND: Sensitized recipients often experience fulminant allograft loss by yet ill-defined cellular and/or humoral immune mechanisms. In this study, we analyzed the contribution of cellular elements, in particular T cells, to the accelerated rejection of renal allografts in sensitized rats. METHODS AND RESULTS: LEW rats sensitized with BN skin grafts died of uremia in 3.3+/-0.9 days after transplantation of a BN kidney, similarly to bilaterally nephrectomized animals. Adoptive transfer of 10(6) graft-infiltrating mononuclear cells as well as their CD25+ subset into otherwise normal LEW recipients accelerated rejection of BN test cardiac allografts (5.4+/-0.5 days to 6.6+/-0.4 days vs. 7.8+/-0.8 days in controls, P<0.0007), while the CD25- population was ineffective (8.0+/-0.6 days, NS). Furthermore, alpha/beta-T-cell receptor (TCR)-targeted therapy with R73 monoclonal antibody abrogated accelerated rejection, and produced long-term survival in sensitized animals treated before kidney engraftment (day -7 to day -1). Long-term survival was associated with an up-regulation of intragraft interleukin-4 and interleukin-10 expression in conjunction with depressed Th-1-type cytokines. In addition, alpha/beta-TCR-targeted therapy even in low subtherapeutic dose decreased IgM alloantibody levels, and prevented the switch from IgM to IgG alloantibody response. CONCLUSIONS: This is the first report that documents the striking efficacy of alpha/beta-TCR-targeted therapy in sensitized rat renal transplant recipients. The results provide evidence for a critical role of T cells for both accelerated rejection and long-term graft survival. Up-regulation of Th2-type cytokine profile may, at least in part, contribute to the acquisition of immune unresponsiveness after alpha/beta-TCR-targeted therapy in this well-defined rat renal transplant model.     

Functional analysis and treatment of cigarette pica

A series of analyses was conducted to assess and treat the pica of cigarette butts by a young man with mental retardation and autism. First, we demonstrated that pica was maintained in a condition with no social consequences when the available cigarettes contained nicotine but not when the cigarettes contained herbs without nicotine. Second, a choice assessment (Fisher et al., 1992) confirmed that tobacco was preferred over the other components of the cigarette (e.g., paper, filter, etc.). Third, an analogue functional analysis (Iwata, Dorsey, Slifer, Bauman & Richman, 1982/1994) demonstrated that cigarette pica was maintained independent of social consequences. Fourth, a treatment designed to interrupt the hypothesized response-reinforcer relationship reduced consumption of cigarettes to zero. Finally, because cigarette pica occurred primarily when the individual was alone or under minimal supervision, a procedure based on stimulus control was developed to improve the effectiveness of the intervention in these situations.     

Periplasmic and fimbrial SefA from Salmonella enteritidis

Salmonella enteritidis produces thin, filamentous fimbriae composed of the fimbrin subunit SefA. Although insoluble in most detergents and chaotropic agents, these fimbriae were soluble at pH 10.5. Furthermore, in sodium dodecyl sulfate, these fibers depolymerized into monomers, dimers and other multimers of SefA, which precipitated on removal of the detergent. In contrast, unassembled periplasmic SefA fimbrins purified from Escherichia coli expressing cloned sefA and sefB were readily soluble in aqueous solution. Fimbrial and periplasmic SefA also differed in their reaction with an anti-SEF14 monoclonal antibody and in their surface hydrophobicity, indicating that the two forms had different properties. Precise mass measurements of periplasmic and fimbrial SefA by mass spectroscopy showed that these variations were not due to post-translational modifications. Periplasmic SefA consisted primarily of intact as well as some N-terminally truncated forms. The main 24 amino acid, N-terminally truncated form of periplasmic SefA was present as a 12.2 kDa monomer which had a low tendency to dimerize whereas intact periplasmic SefA was present as a 34.1 kDa homodimer. Intact periplasmic SefA also formed stable multimers at low concentrations of chemical cross-linker but multimerization of the truncated form required high concentrations of protein or cross-linker. Thus, SefA fimbrins appear to multimerize through their N-termini and undergo a conformational change prior to assembly into fibers. Within these fibers, subunit-subunit contact is maintained through strong hydrophobic interactions.     

Molecular genetics. Introduction

While sharing the same techniques as the field at large, diagnostic molecular genetics is unique among the subdisciplines of molecular pathology in many of its aspects, from sample collection to ethical implications of the test results obtained. Yet, despite its many challenges, this branch of DNA diagnostics has already pervaded the practice of medical genetics to an extent unmatched in any other clinical specialty. Genetic disease also presents the most immediately obvious opportunities for extension from DNA-based diagnosis to DNA-based therapy.     

Apyrase administration prolongs discordant xenograft survival

Platelet thrombi and vascular inflammation are prominent features of discordant xenograft rejection. The purinergic nucleotides ATP and ADP, which are secreted from platelets and released by injured endothelial cells (EC), are important mediators of these reactions. Quiescent EC express the ectoenzyme ATP-diphosphohydrolase (ATPDase; an apyrase), which exerts an important thromboregulatory function by hydrolyzing both ATP and ADP. We have shown that ATPDase activity is rapidly lost from the surface of the EC following ischemia-reperfusion injury and during xenograft rejection. The aim of this study was to supplement ATPDase activity within xenografts by infusion of soluble apyrases, and thereby validate the importance of local ATPDase activity in the modulation of xenograft rejection. Lewis rats underwent heterotopic cardiac xenografting from guinea pigs and apyrase was administered intravenously (200 U/kg) as a single dose to evaluate effects on hyperacute rejection (HAR). This initial dose was followed by a continuous apyrase infusion (8.0 U/kg/hr) directly into the graft aorta in combination with systemic cobra venom factor (CVF) administration to deplete complement when delayed xenograft rejection (DXR) was studied. Functional apyrase levels in vivo were assessed by the capacity of blood samples taken at the time of surgery and rejection to inhibit platelet aggregation in vitro. Apyrase administration significantly prolonged graft survival in HAR and DXR. Functional assays showed inhibition of platelet aggregation suggesting effective systemic antiaggregatory effects of the administered apyrases. Histologic studies showed that apyrase administration abrogated local platelet aggregation and activation in HAR and DXR. Our data demonstrate that local administration of apyrase prolonged discordant xenograft survival. These observations emphasize the potential importance of purinergic mediators in platelet activation during xenograft rejection.     

The pial ligaments of the anterior spinal artery and their stretch receptors. A spinal cord distraction-sensing system?

The pial sheath of the anterior spinal artery displays a system of ligaments that course along the ventral surfaces of the anterior spinal artery and its medullary feeder arteries on the lower half of the spinal cord. Frequently, discrete ligamentous straps extend from these anterior spinal artery ligaments to the sheath of an anterior spinal nerve root to reinforce the general cauda equina pial connections to this system. Microscopy of ligament sections revealed that numerous Golgi-type neurofascicular receptors were oriented longitudinally among the ligament fascicles and associated with well-myelinated nerves. As this type of mechanoreceptor has been known only in association with stretch reflex mediation in the musculoskeletal system, it appeared likely that these anterior spinal artery ligaments and their homologous type of receptors may be implicated in sensing distraction of the thoracolumbar spinal cord and protectively modifying the actions of the involved spinal musculature.