Depressed mediator release by inflammatory exudate cells in immunized rats following antigen challenge

The aim of the present study was to characterize leukocytes present in a local inflammatory reaction with respect to production of prostaglandin E (PGE) and the release of factors affecting lymphocyte function, which are produced by macrophages (interleukin-1) or stimulated lymphocytes (interleukin-2). Lewis rats immunized against bovine serum albumin (BSA) were challenged by intraperitoneal injection of antigen. The PGE release by peritoneal cells (PEC) was testedin vitro and found to be enhanced in immunized rats before BSA challenge. However, PEC harvested after the injection of antigen showed a marked reduction in prostaglandin production during the first 24 h. When these cells were tested for the secretion of lymphokines (IL-1, IL-2) the same depression was found.     

Expression of the endothelial markers PECAM-1, vWf,and CD34 in vivo and in vitro

EC culture models are essential to study pathological alterations of endothelial cells (ECs) in pulmonary vascular diseases under standardized conditions. Nevertheless, little is known about the spectrum of alterations of vessel-specific endothelial phenotypes in monolayer cultures. For the comparative study of endothelial markers in vivo and in vitro we investigated immunohistochemically the expression of PECAM-1, vWf, and CD34 by pulmonary ECs in vivo and in stimulated/unstimulated human umbilical vein endothelial cells (HU-VEC) and human pulmonary microvascular endothelial cells (HPMEC). In vivo, vessel type-specific expression patterns were found for vWf and CD34, while PECAM-1 was homogeneously and strongly expressed. While all HUVEC showed a marked vWf staining, about two-thirds of HPMEC exhibited a strong and the rest a moderate vWf staining. In both in vitro models all ECs were clearly PECAM-1-positive. However, only about 20% of the HUVEC and HPMEC were CD34-positive. Our results demonstrate the reduced expression of vessel type-specific endothelial phenotypes by endothelial monolayer cultures, stressing the need to improve culture conditions as well as develop cocultures and three-dimensional culture models. Moreover, the need for endothelial markers specific for single microvascular type ECs becomes obvious in order to establish cultures consisting of only one microvascular ECs subpopulation.     

Differential expression of APO-1 on human thymocytes: Implications for negative selection?

Negative selection during T cell ontogeny involves selective induction of apoptosis in thymocytes. In peripheral lymphoid cells, apoptosis may be mediated via the APO-1 pathway. Here we report that APO-1 is constitutively expressed on the vast majority of human thymocytes but down-regulated at a mature stage of thymocyte development (TCR^hi). This stage of development is characterized by CD28^hi, CD44^hi, CD69^hi and up-regulation of Bcl-2 protein. We define a new thymocyte subpopulation that expresses high levels of APO-1 and intermediate levels of T cell receptor α/β (TCR^im/APO-1^hi). The TCR^im/APO-1^hi population contains a large fraction of dead cells, suggesting that the APO-1 pathway may be involved in negative selection of at least a fraction of thymocytes after intrathymic activation.     

Pelvic and lower extremity arterial imaging: diagnostic performance of three-dimensional contrast-enhanced MR angiography

OBJECTIVE: The diagnostic performance of a three-dimensional MR angiography-based strategy was assessed with regard to its ability to characterize the arterial vasculature from the aortic bifurcation to the lower extremity runoff vessels. A single-injection, two-station protocol in combination with a lower-extremity vascular coil was used. SUBJECTS AND METHODS: Both conventional digital subtraction angiography and three-dimensional contrast-enhanced MR angiography with a dedicated peripheral vascular coil were performed in 61 patients with suspected peripheral vascular disease. In a prospective analysis, one reviewer evaluated the digital subtraction angiographic images and a second reviewer evaluated the MR angiographic images; both were unaware of the results of the other imaging technique. Each vascular segment (29 segments per patient) was evaluated for the presence of occlusive vessel disease. The following grading system was applied: 0, normal; 1, vessel irregularity with a luminal reduction of less than 10%; 2, mild stenosis (lumen reduction, 10-49%); 3, severe stenosis (lumen reduction, 50-99%); and 4, occlusion (lumen reduction, 100%). In 11 patients surgical graft patency was assessed. RESULTS: MR angiography provided an image quality comparable with that of digital subtraction angiography. Overall sensitivity and specificity for MR angiography were 92% and 96.6%, respectively, for the detection of hemodynamically significant disease and 92.3% and 99.4%, respectively, for the detection of occlusions. CONCLUSION: Two-station contrast-enhanced three-dimensional MR angiography with a dedicated lower-extremity vascular coil proved effective enough to consider it as a noninvasive alternative to digital subtraction angiography in the assessment of the pelvic and lower extremity arterial vasculature.