The biology of Stat4 and Stat6.

IL-4 and IL-12 are cytokines that are important regulators of the proliferation, differentiation and functional capacity of lymphocytes. STATs (signal transducers and activators of transcription) are transcription factors that provide a direct link between the cytokine receptors and cytokine induced gene transcription. Stat6 and Stat4 are two STAT family members that specifically mediate signals that emanate from the IL-4 and IL-12 receptors, respectively. Recently a great deal of progress has been made in understanding the specific roles that Stat6 and Stat4 play in lymphocyte function through in vitro as well as in vivo studies using Stat6 and Stat4-deficient mice. This report will summarize and describe the recent advances made in understanding the activation and regulation of Stat6 and Stat4 as well as their roles in the development of an immune response. Oncogene (2000).

Stat6-dependent and -independent pathways for IL-4 production.

Stat6 has been shown to have a crucial role in the IL-4-dependent differentiation of Th2 cells. In this report, we explore whether in vitro Th2 differentiation driven by altered costimulatory signals or Ag dose is Stat6 dependent. We find that blocking B7-1 signaling in vitro promotes the differentiation of IL-4-secreting Th2 cells in wild-type but not Stat6-deficient T cell cultures. Additionally, stimulation with peptide Ag doses that normally result in the production of Th2 cells in vitro fails to do so in cultures of Stat6-deficient cells. We also demonstrate that Stat6 is required for the in vitro differentiation of CD8+ T cells into IL-4-secreting cytotoxic T cell type 2 cells. However, IL-4 expression is not absolutely dependent on Stat6. We demonstrate that populations of T cells that do not require IL-4 for their development, such as NK T cells, are still competent to secrete IL-4 in the absence of Stat6. These results demonstrate that Stat6 is required for the differentiation program leading to the generation of Th2 and cytotoxic T cell type 2 cells but not for IL-4 expression in cells that do not undergo differentiation in response to IL-4.

A signal transducer and activator of transcription (Stat)4-independent pathway for the development of T helper type 1 cells.

The differentiation of T helper (Th) cells is regulated by members of the signal transducer and activator of transcription (STAT) family of signaling molecules. We have generated mice lacking both Stat4 and Stat6 to examine the ability of Th cells to develop in the absence of these two transcription factors. Stat4, Stat6(-/-) lymphocytes fail to differentiate into interleukin (IL)-4-secreting Th2 cells. However, in contrast to Stat4(-/-) lymphocytes, T cells from Stat4, Stat6(-/-) mice produce significant amounts of interferon (IFN)-gamma when activated in vitro. Although Stat4, Stat6(-/-) lymphocytes produce less IFN-gamma than IL-12-stimulated control lymphocytes, equivalent numbers of IFN-gamma-secreting cells can be generated from cultures of Stat4, Stat6(-/-) lymphocytes activated under neutral conditions and control lymphocytes activated under Th1 cell-promoting conditions. Moreover, Stat4, Stat6(-/-) mice are able to mount an in vivo Th1 cell-mediated delayed-type hypersensitivity response. These results support a model of Th cell differentiation in which the generation of Th2 cells requires Stat6, whereas a Stat4-independent pathway exists for the development of Th1 cells.

Comparison of open and thoracoscopic bilateral volume reduction surgery: complications analysis.

BACKGROUND: The effectiveness of lung volume reduction for the treatment of patients with emphysema is well established, but data about the surgical approach, the postoperative management, and complications are limited. We report a comparison of patients undergoing bilateral lung volume reduction (BLVRS) via median sternotomy and thoracoscopic techniques with emphasis on hospital course and complications. METHODS: All patients undergoing BLVRS at Hospital of University of Pennsylvania were analyzed for mortality and morbidity, using a combination of prospective data analysis and retrospective chart review. RESULTS: Patients undergoing BLVRS via median sternotomy were older than those undergoing video-assisted thoracoscopic surgery (VATS) procedures (63.9+/-6.89 vs 59.3+/-9.4 years, p = 0.005). Operating time was longer for the VATS procedure (147 versus 129 minutes, p = 0.006) while estimated blood less was greater for median sternotomy (209 versus 82 L, p = 0.0000017). Significant differences were found in intensive care unit stay, days intubated, life-threatening complications, respiratory complications, requirement for tracheostomy, and death that favored VATS BLVRS. When only later cohorts of patients were compared, more life-threatening complications and deaths were found in patients undergoing BLVRS by median sternotomy. There were no differences between early and late median sternotomy BLVRS patients. Twenty-six percent of the lethal complications in median sternotomy BLVRS patients were bowel perforations, equally divided between duodenal ulcers and colons. CONCLUSIONS: Managing patients after BLVRS remains complex. Bilateral video-assisted volume reduction offers equivalent functional outcome with potentially decreased morbidity and mortality. Gastrointestinal perforations can complicate the management of these patients.

GI complications after orthotopic lung transplantation.

OBJECTIVES: Recently, lung transplantation has been performed with increasing frequency and improved outcomes. GI complications have been observed and reported in patients undergoing cardiac and renal transplantations but only recently have been reported in patients after lung transplantation. No large cohort has been systematically analyzed for all GI complications after lung transplantation. The present study describes, categorizes, and assesses risk factors for the development of such GI complications. METHODS: Records of 45 patients who underwent 47 single or bilateral orthotopic lung transplants between November 1991 and January 1994 were reviewed. RESULTS: Twenty-three patients (51%) had 64 GI complications requiring 13 operations on eight patients. The incidence of major abdominal procedures in the entire transplant cohort was 18% (8/45). Their operative mortality rate was 63% (5/8). Eighteen different types of nonoperative complications occurred and were subclassified into major and minor complications. Complications were defined as major if they required medical or surgical intervention and altered patient management. Most GI complications (73%) occurred within 1 month after transplantation. No risk factors were identified to ascertain who will develop GI complications. CONCLUSIONS: GI complications occur in more than one-half of lung transplant recipients early after transplantation and in the absence of identifiable risk factors. Because there are no precedent risk factors to suggest who will develop GI complications, clinicians must be alert to any warning signs and symptoms. The majority of complications are nonoperative, responding to conservative therapy, but there is a higher overall mortality rate for patients requiring operative intervention, necessitating an aggressive search for major, life-threatening complications in these immunosuppressed patients.

Analysis of Epstein-Barr virus-associated posttransplantation lymphoproliferative disorder after lung transplantation.

BACKGROUND: Epstein-Barr virus (EBV)-associated posttransplantation lymphoproliferative disorder (PTLD) is a serious complication of lung transplantation. Besides immunosuppression the risk factors for PTLD development are largely unknown. METHODS: The incidence of PTLD was ascertained in a lung transplant population consisting of 45 patients. Nine patients (20%) experienced PTLD. The clinical, histologic, and human leukocyte antigen (HLA) data were collected on all patients. The incidence of EBV infection in lymphoid tissue taken at the time of engraftment was studied by using EBV in situ hybridization. RESULTS: All patients with PTLD had polymorphous lymphoproliferations, seven of which were polymorphous B-cell hyperplasias and two of which were polymorphous B-cell lymphomas. EBV was identified in all lesions. All patients with polymorphous B-cell hyperplasias had clinically unsuspected disease, five of which were identified at autopsy. The two polymorphous B-cell lymphoma lesions were monoclonal and regressed with immunosuppression reduction. EBV in situ hybridization on donor or recipient lymph nodes obtained at engraftment from the 45 transplant recipients showed no difference in the number of EBV positive cells in patients with and without PTLD. Cyclosporine and PTLD and azathioprine dosages and cyclosporine levels were similar between patients with and without PTLD. PTLD was seen in patients with high cumulative doses of antilymphocyte globulin. Analysis of HLA status showed a predominance of HLA A2 and DR7 in the donors of the patients with PTLD, whereas donor HLA B7 was more common in patients without PTLD> CONCLUSIONS: Detailed studies are necessary to further elucidate the risk factors for PTLD development in the lung transplant population.

Elf-1 binds to a critical element in a second CD4 enhancer.

The coordinated expression of CD4 and CD8 during T-cell development is tightly coupled with the maturation state of the T cell. Additionally, the mutually exclusive expression of these receptors in mature T cells is representative of the functional T-cell subclasses (CD4+ helper T cells versus CD8+ cytotoxic T cells). We have studied the regulation CD4 gene transcription during T-cell development in an attempt to gain an understanding of the molecular mechanisms involved in T-cell development and differentiation. Here we present the identification of a second transcriptional enhancer in the murine CD4 locus 24 kb upstream of the CD4 promoter. This enhancer is active in mature T cells and is especially active in CD4+ helper T cells. A number of nuclear proteins bind to elements in the minimal CD4 enhancer that includes consensus sites for AP-1, Sp1, Gata, and Ets transcription factor families. We find that the Ets consensus site is crucial for enhancer activity and that the recently identified Ets factor, Elf-1, which is expressed at high levels in T cells and involved in the regulation of several other T-cell-specific genes, is a dominant protein in T-cell nuclear extracts that binds to this site.

A transcriptional silencer controls the developmental expression of the CD4 gene.

The appropriate expression of the CD4 glycoprotein is required for T-cell function and development. Here we define the transcriptional control elements in the CD4 locus that convey CD(4+)-specific expression of a marker gene in transgenic mice. Using nuclear run-on experiments, we have determined that the major mechanism for CD4 expression control during development is transcriptional. We have identified a developmental stage- and tissue-specific negative regulatory element in the first intron of the murine CD4 gene that has the characteristics of a transcriptional silencer. The CD4 silencer functions to inhibit marker gene expression at two different stages of T-cell development, as well as in non-T hematopoietic cells, and thus is the critical controlling element responsible for T-cell-specific, as well as developmental- and subclass-specific, expression.

Surgical critical care for cancer patients.

Progress in cancer surgery and changes in philosophy have resulted in greater numbers of critically ill surgical oncology patients. The effects of cancer and prior exposure to cancer therapies increase the risks for postsurgical problems. Life-threatening cardiopulmonary sequela and patients undergoing liver resections and transplantation are examples of problems that require the knowledge and skill of critical care nurses. Critical care surgical nurses face new challenges by merging their surgical nursing expertise with principles of cancer care.

Guidelines for selecting a conceptual model of nursing: focus on the individual patient.

How do conceptual models help you in clinical practice? How can you select the best model to guide successful interventions for your critical care patients? These authors present three guidelines for selection of a conceptual model for your patient situation. Six case studies of patients requiring critical care nursing demonstrate the fit of the patient's problems and goals for care with particular conceptual models of nursing.

Cell surface distribution of endogenous and effects of exogenous gangliosides on neuronal survival, cell shape and growth in vitro.

In vitro immunostaining of neurons from spinal cord or brain of embryonic chicken by means of monoclonal anti-ganglioside antibodies (Q211, D21b) revealed a fluorescence-labeling of c-polysialogangliosides and GD1b evenly distributed over the entire neuronal surface including filopodia at the growth cones. On electronmicroscopical level the gold-stained ganglioside-antigens were found more or less densely packed in small adjacent areas suggesting a concentration in local "domains". Survival in serum-free or serum-containing medium of embryonic spinal cord motoneurons, which normally died if not cultivated in muscle conditioned medium or in contact to myotubes, was remarkably improved in the presence of a ganglioside mixture (10 microM) from bovine brain. If embryonic neurons from optic lobes were cultivated at low Ca(2+)-concentration (< 20 microM) they developed flat, broad cell bodies with many filopodia and only a few flat-shaped short processes. A very weak cytoskeleton-staining by means of rhodamine-linked phalloidine indicated that polymerization of actin was impaired in these neurons. At the same low Ca(2+)-concentration of < 20 microM but in the presence of ganglioside GM1 (up to 100 microM) most of the neurons developed a "normal" cell shape with rounded perikarya and thin neurites with "normal" shaped growth cones. In this case rhodamine-linked phalloidine revealed a much more intense staining mainly concentrated within the growing tips. The morphology and growth of the ganglioside-treated neurons resembled that of neurons cultivated at a higher Ca(2+)-concentration of at least 600 microM.

Expression of the CD4 gene requires a Myb transcription factor.

We have analyzed the control of developmental expression of the CD4 gene, which encodes an important recognition molecule and differentiation antigen on T cells. We have determined that the CD4 promoter alone functions at high levels in the CD4+ CD8- mature T cell but not at the early CD4+ CD8+ stage of T-cell development. In addition, the CD4 promoter functions only in T lymphocytes; thus, the stage and tissue specificity of the CD4 gene is mediated in part by its promoter. We have determined that a Myb transcription factor binds to the CD4 promoter and is critical for full promoter function. Thus, Myb plays an important role in the expression of T-cell-specific developmentally regulated genes.