The development of cellular immunity to Epstein-Barr virus after allogeneic bone marrow transplantation

Epstein-Barr virus-induced lymphoproliferative disease (EBV-LPD) is a potentially lethal complication during the first 6 months after allogeneic bone marrow transplantation (BMT). To determine whether deficiencies of EBV-specific cellular immunity contribute to EBV-LPD susceptibility and distinguish patients at risk, we performed limiting dilution analysis to quantify anti-EBV cytotoxic T-lymphocyte precursor (CTLp) frequencies in 26 recipients of unmodified or T-cell-depleted (TCD) grafts from EBV-seropositive donors. At 3 months post-BMT (n = 26), only five patients had EBV CTLp frequencies in the range of seropositive normal controls, irrespective of the type of transplant administered. By 6 months post-BMT, 9 of 13 patients tested had EBV CTLp frequencies within the normal range. The time period in which these patients had deficient cellular immunity to EBV corresponds to the period in which we have observed EBV-LPD in most prior patients. One patient with a low EBV CTLp frequency at 4 months post-BMT developed an EBV-LPD. Within 2 weeks of receiving an infusion of donor peripheral blood mononuclear cells (PBMC) providing less than 1,200 EBV- specific cytotoxic T-cell precursors, populations of EBV-specific CTL in the circulation were restored to levels detected in normal seropositive adults. Concurrently, the patient achieved a regression of the EBV-LPD, which has been sustained without further therapy. These studies indicate that recipients of both unmodified and TCD marrow grafts have profound deficiencies of EBV-specific T cell-mediated immunity early posttransplant, and that the period of risk for EBV-LPD closely corresponds to this interval of severe deficiency. Treatment of one patient with EBV-LPD with marrow donor-derived PBMC induced a rapid expansion of EBV-specific cytotoxic T-cell populations that occurred contemporaneously with the clinical regression of disease.     

The factor V B-domain provides two functions to facilitate thrombin cleavage and release of the light chain

Blood coagulation factors V and VIII are homologous proteins that have the domain organization A1-A2-B-A3-C1-C2. Upon thrombin activation, the B-domains of both molecules are released. Previous studies on factor VIII showed that the B-domain was not required for thrombin cleavage or activity. In contrast, deletion of the factor V B-domain (residues 709 to 1545) yielded a molecule with sevenfold reduced procoagulant activity that was not cleaved by thrombin. However, this factor V B- domain deletion molecule was activated by factor Xa, although the fold- activation was 85% that of wild-type factor V. Thrombin cleavage of factor V occurs initially after residue 709 and subsequently after residues 1018 and 1545. The requirement for thrombin cleavage within the B-domain at residue 1018 was evaluated by mutagenesis of Arg1018 to Ile. In the resultant R1018I mutant, the rate of thrombin activation and appearance of maximal cofactor activity was delayed and was consistent with delayed cleavage of the light chain at residue 1545. In contrast, the rate of factor Xa activation in the R1018I mutant was not altered. This finding suggests that thrombin cleavage at 1018 facilitates subsequent thrombin cleavage at 1545. Further mutagenesis was used to study the requirement for sequences within the factor V B- domain for thrombin cleavage at residue 1545. Whereas the factor V deletion molecule removing residues 709 to 1545 was not cleaved by thrombin, a smaller B-domain deletion molecule (residues 709 to 1476) containing an acidic amino acid-rich region (residues 1490 to 1520) was effectively cleaved by thrombin. These results show that residues 1476 to 1545, which contain an acidic amino acid-rich region, were required for thrombin cleavage of the light chain. Introduction of an acidic amino acid-rich region from factor VIII (residues 337 to 372) into the factor V 709 to 1545 deletion also restored thrombin cleavage of the light chain. In contrast, similar replacement with the acidic region from the factor VIII light chain (residues 1649 to 1689) was significantly less effective in promoting thrombin cleavage of the light chain. This finding suggests that the different acidic regions in factors V and VIII are not functionally equivalent in their interaction with thrombin.(ABSTRACT TRUNCATED AT 400 WORDS)     

Organization of the gene for human platelet/endothelial cell adhesion molecule-1 shows alternatively spliced isoforms and a functionally complex cytoplasmic domain

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a cell-cell adhesion molecule that is expressed on circulating platelets, on leukocytes, and at the intercellular junctions of vascular endothelial cells and mediates the interactions of these cells during the process of transendothelial cell migration. The cDNA for PECAM-1 encodes an open reading frame of 738 amino acids (aa) that is organized into a 27- aa signal peptide, a 574-aa extracellular domain composed of 6 Ig homology units, and a relatively long cytoplasmic tail of 118 aa containing multiple sites for posttranslational modification and postreceptor signal transduction. To provide a molecular basis for the precise evaluation of the structure and function of this transmembrane glycoprotein, we have determined the organization of the human PECAM-1 gene. The PECAM-1 gene, which has been localized to human chromosome 17, is a single-copy gene of approximately 65 kb in length and is broken into 16 exons by introns ranging in size from 86 to greater than 12,000 bp in length. Typical of other members of the Ig superfamily, each of the extracellular Ig homology domains is encoded by a separate exon, consistent with PECAM-1 having arisen by gene duplication and exon shuffling of ancestral Ig superfamily genes. However, the cytoplasmic domain was found to be surprisingly complex, being encoded by seven short exons that may represent discrete functional entities. Alternative splicing of the cytoplasmic tail appears to generate multiple PECAM-1 isoforms that may regulate phosphorylation, cytoskeletal association, and affinity modulation of the mature protein. Finally, a processed pseudogene having 76% identity with PECAM- 1 cDNA was identified and localized to human chromosome 3. These findings should have important implications for structure/function analysis of PECAM-1 and its role in vascular adhesive interactions.     

Orofacial neuralgia associated with a middle cerebral artery aneurysm

Chronic orofacial pain of neuropathic origin can present diagnostic and management dilemmas to dental practitioners and also affects the patient's quality of life. Intracranial aneurysms are a potential cause of stroke (e.g. sub‐arachnoid haemorrhage) that is usually associated with, high rates of mortality and morbidity. A patient who had been previously managed for symptoms of temporomandibular joint disorder (TMD) presented with sharp, shooting pain of moderate intensity. It was precipitated by swallowing, and radiated to the right throat, posterior border of the mandible, ear and temporomandibular joint. Clinical and radiological investigations ruled out odontogenic pain, TMD and other more common types of facial pain. Magnetic resonance imaging revealed a 7 × 6 mm aneurysm in the right middle cerebral artery (MCA) which was subsequently surgically clipped. Interestingly, the facial pain resolved after this procedure. Compression of the insular region of the brain innervated by the trigeminal, glossopharyngeal and vagus nerves provides a plausible explanation for the pain reported. To our knowledge, this is the first case of facial neuralgia associated with an aneurysm in the MCA which emphasizes the importance of a multidisciplinary approach in the diagnosis and management of unusual cases of chronic orofacial pain.     

Foreign body removal with fine-nosed forceps and assistance of image intensification

Foreign body removal has been developed as a routine radiology department service. Techniques, indications and hazards are described.     

Unusual presentation of perirenal lung metastases

Lung cancer is not commonly known to metastasise to the perirenal space, with only five such cases previously published. We present an unusual case of perirenal lung metastases manifesting as diffuse perinephric stranding which to our knowledge has not been described before.     

Breast cancer cell lines: friend or foe?

The majority of breast cancer research is conducted using established breast cancer cell lines as in vitro models. An alternative is to use cultures established from primary breast tumours. Here, we discuss the pros and cons of using both of these models in translational breast cancer research.     

Paracetamol use, availability, and knowledge of toxicity among British and American adolescents

Paracetamol is the commonest agent employed in self poisoning, however it is not clear whether adolescents possess insight into the serious complications associated with its misuse. Using a one page questionnaire, the availability, usage, and knowledge of toxicity of paracetamol among 1147 American and British adolescents was assessed. Although 90% of all students recognised that paracetamol could kill, the great majority of students overestimated the lethal dose. In addition, while knowledge regarding side effects of paracetamol was poor the drug was widely available to, and used by, the study population. It is proposed that gross overestimation of the number of tablets required to kill, poor understanding of paracetamol side effects, and wide availability of the drug contribute to its frequent use in adolescent suicidal behaviour. The inclusion of some over-the-counter medications in school drug education programs in addition to tighter control of the availability of paracetamol may help reduce the problem of adolescent self poisoning.     

Screening for a raised rectal temperature in Africa

The main purpose of this study was to compare rectal and axillary temperature measurements in African children. Altogether 573 sick children were seen in an outpatient setting in rural West Africa. Rectal and axillary temperatures were measured and the parent or guardian was asked if they thought that the child had a raised body temperature. Normal ranges were defined from an age matched population of 203 healthy children. A raised axillary temperature predicted a raised rectal temperature with a sensitivity of 98% and a specificity of 88%. The parents' impression that their child had a fever was a less sensitive (89%) and less specific (59%) indicator of raised rectal temperature. A raised axillary temperature is a good screening test for a raised rectal temperature in African children.