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W Mark

Publications and source records attributed to W Mark.

28 records · Page 2Linked to original sources
PubMed1996

T cell independence of macrophage and natural killer cell infiltration, cytokine production, and endothelial activation during delayed xenograft rejection.

Rejection of guinea pig cardiac grafts in rats depleted of complement takes place in 3-4 days and involves progressive mononuclear cell infiltration and cytokine expression, fibrin and antibody deposition, and endothelial cell up-regulation of adhesion and procoagulant molecules, a process termed delayed xenograft rejection (DXR). The relative contribution of each effector mechanism and the role of T cells in this complex process are unknown, although small numbers of interleukin (IL) 2 receptor-positive T cells are present at the time of rejection. We investigated the importance of T cells in DXR by comparing discordant xenograft responses of nude rats, which lack T cell receptor (TCR)-alpha/beta+ cells, with those of normal Lewis rats. Nude or Lewis rats receiving guinea pig cardiac grafts were assigned to one of three groups: no therapy, daily administration of cobra venom factor (CVF), or splenectomy plus daily CVF. All untreated rats rejected their xenografts within 10-15 min, whereas grafts in complement-depleted recipients survived a further 3-4 days; splenectomy had no significant additional effect upon graft survival. Immunohistologic analysis in CVF-treated nude recipients with or without splenectomy showed: (1) considerable leukocyte infiltration of xenografts (mean +/- SD, 76+/-14 and 71+/-16 leukocytes/field, respectively, at 72 hr, compared with 68+/-17 in Lewis rats), consisting largely of macrophages (>75% of total leukocytes) plus small numbers of natural killer cells (10-20%) with no detectable B or T cells (TCR-alpha/beta or TCR-gamma/delta); (2) at least 10-fold lower levels of intragraft IgM or IgG deposition than in corresponding Lewis recipients; and (3) considerable cytokine expression by intragraft macrophages (IL-12, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, IL-1beta, IL-6, IL-7, IL-12) and natural killer cells (interferon-gamma), as well as up-regulation of tissue factor expression and dense fibrin deposition. Analysis of recipient sera of both control and nude rats by ELISA, for the binding of IgG or IgM to guinea pig platelets, showed a rapid rise after transplantation in the titers of IgM and IgG antibodies, which was abrogated by prior splenectomy; i.e., data from splenectomized xenograft recipients reflect the presence of only basal levels of IgM and IgG. Thus, our data in nude rats show rejection times and intragraft features of DXR comparable to those in immunocompetent Lewis recipients, despite a lack of detectable host T cells, and, in the case of splenectomized rats, only about one tenth of normal xenoreactive antibody levels. Our data document a new model in which to analyze the immunopathogenesis of DXR.

Animals↗
PubMed1993

Pluripotency of cultured rabbit inner cell mass cells detected by isozyme analysis and eye pigmentation of fetuses following injection into blastocysts or morulae.

Pluripotency of isolated rabbit inner cell masses (ICMs) and cultured (3 days) inner cell mass (ICM) cells was tested by injecting these donor cells into day 3.5 blastocysts (experiment 1) or day 3 morulae (experiment 2) to produce chimeric embryos. Injected (n = 107) and noninjected (n = 103) embryos were transferred to the opposite uterine horns of the same recipient females. Chimerism was determined by adenosine deaminase (ADA) isozyme analysis on fetal tissue and by eye pigmentation at midgestation. In experiment 1, 53% and 64%, respectively, of blastocysts injected with ICMs or cultured ICM cells developed to midgestation, compared with 52% and 48% for controls. Of these fetuses, four (31%) and one (6%), respectively, had ADA chimerism. In experiment 2, 38% and 62%, respectively, of the morulae injected with ICMs or cultured ICM cells developed to midgestation, compared with 46% and 56% for control morulae. Six (43%) chimeric fetuses from morulae injected with ICMs were detected by ADA analysis, but 12 (86%) chimeric fetuses were detected by eye pigmentation, indicating that eye pigmentation was a more sensitive marker for chimerism than our ADA assay. None of the 14 fetuses recovered after injecting morulae with cultured ICM cells were chimeric with either marker. No chimeras developed from control embryos. These studies demonstrate 1) that pregnancy rates are not compromised by injection of blastocysts or morulae with ICMs or cultured ICM cells, 2) that chimeric rabbit fetuses can be produced by injecting ICMs into either blastocysts or morulae, and 3) that cultured ICM cells can contribute to embryonic development when injected into blastocysts.

Animals↗
PubMed1984

Transforming functions associated with Epstein-Barr virus.

Epstein-Barr virus (EBV) transforms the human B-lymphocytes it infects into lymphoblasts that are competent to proliferate indefinitely in tissue culture [1]. The dividing transformed lymphoblasts carry multiple and complete copies of EBV DNA as plasmids [1]. No viral functions that are necessary for EBV-induced transformation have been identified and characterized to date. We have developed an assay that aids in the identification of viral functions needed to maintain the viral plasmid in transformed cells. The assay employs a plasmid vector that encodes resistance to ampicillin and can replicate in E. coli. It also encodes resistance to the neomycin derivative G418, so that its presence can be selected in mammalian cells [2]. Fragments of viral DNA that span the genome have been molecularly cloned into this vector. These recombinant molecules have been transfected into four cell types, and survivors to G418 have been scored. The DNA from one region of EBV gives a 10- to 100-fold higher rate of survival per microgram of added DNA than does the DNA from all other recombinants, as tested in cells that already contain EBV genomes. This recombinant fragment of EBV is maintained in an apparently unrearranged state as a plasmid and therefore carries at least those cis-acting viral elements necessary for plasmid replication.

B-Lymphocytes↗
PubMed1977

Clonal transformation of adult human leukocytes by Epstein-Barr virus.

We have developed a clonal transformation assay for Epstein-Barr virus which uses adult human leukocytes as target cells. The target cells were isolated from Epstein-Barr seronegative donors, and the same donor's cells could be studied repeatedly over long periods of time. When these cells were transformed by Epstein-Barr virus and had proliferated sufficiently to be studied, they had an average cloning efficiency of 3%. Assuming this average cloning efficiency obtains at the onset of transformation, we calculate that transformation by Epstein-Barr virus leads to immortalization maximally of about 1 in 30 of the adult peripheral leukocytes exposed to the virus. Studying the number of colonies transformed as a function of the amount of virus to which the cells are exposed indicates that a single DNA-containing virus particle is sufficient to transform a cell. All of the transformed clones studied harbored viral DNA. This technique will now permit, for the first time, our studying clonal variations in adult peripheral leukocytes transformed by Epstein-Barr virus as a function of input multiplicity of the virus and of the donor's immune status.

Adult↗
PubMedDate not supplied

Simultaneous pancreas-kidney transplantation in a large multicenter study: surgical complications.

UNLABELLED: Simultaneous pancreas-kidney (SPK) transplantation has evolved as an effective treatment modality for patients with end-stage nephropathy owing to type 1 diabetes mellitus. This kidney-pancreas transplant procedure includes a number of risks, one of them being surgical complications, which were analyzed in this large prospective multicenter study. PATIENTS AND METHODS: The analysis included 205 patients randomly assigned to tacrolimus (n = 103) or cyclosporine ME (n = 102) in the Euro-SPK001 study. Surgical complications were defined as any intervention in the postoperative course related to the transplant procedure. RESULTS: The number of patients undergoing relaparotomy was significantly lower among the tacrolimus group (26.2%) as compared to the cyclosporine ME group (43.1%, P = .0109). Relaparotomy was performed earlier in the cyclosporine ME group (day 14 +/- 17) compared to patients in the tacrolimus group (day 26 +/- 26, P = .0506). Graft vessel thrombosis, intra-abdominal hemorrhage, and enteric or ureteral leakage within the first 3 months occurred significantly more frequently in cyclosporine ME-treated patients. Donor age above 45 years showed a negative impact on surgical complications. Relaparotomy had no impact on patient survival but significantly affected pancreas and kidney graft survival in both groups. CONCLUSION: This prospective, randomized, multicenter trial in patients undergoing primary SPK demonstrated a benefit of tacrolimus over cyclosporine ME with regard to the incidence of surgical complications and, consecutively, to kidney and pancreas graft survival.

Diabetes Mellitus, Type 1↗