Improved adhesion and proliferation of human endothelial cells on polyethylene precoated with monoclonal antibodies directed against cell membrane antigens and extracellular matrix proteins.

Endothelial cell seeding may improve the patency of synthetic vascular grafts provided that platelet reactivity of nonendothelialized sites is not increased. We have investigated if surface-adsorbed monoclonal antibodies directed against endothelial cell membrane proteins and against extracellular matrix proteins promote the adhesion and proliferation of cultured human endothelial cells, without causing platelet deposition at non-endothelialized sites. Adhesion of endothelial cells onto polyethylene coated with monoclonal antibodies directed against endothelial cell-specific membrane antigens, integrin receptors and glycoprotein CD31 was equal to or higher than adhesion onto fibronectin-coated polyethylene. Endothelial cells did not proliferate on these surface-adsorbed antibodies. However, pre-coating of polyethylene with mixtures of endothelial cell-specific monoclonal antibodies and monoclonal antibodies directed against fibronectin or von Willebrand factor, resulted in relatively high adhesion and optimal proliferation. Platelet reactivity of the polyethylene surface was found to significantly increase after adsorption of fibronectin, endothelial cell-specific monoclonal antibody or its Fc fragments. In contrast, adsorption of F(ab')2 fragments of endothelial cell-specific monoclonal antibody did not promote platelet deposition. Therefore, it is concluded that coating of vascular graft materials with mixtures of F(ab')2 fragments of monoclonal antibodies specifically directed against endothelial cells and against extracellular matrix proteins may be an effective way to both promote the growth of seeded endothelial cells and limit platelet-graft interaction.     

Teaching the plantar reflex.

The efficacy of an instructional videotape about the interpretation of the plantar response was evaluated during a two week neurological clerkship. Experimental groups saw the videotape, control groups did not. All students (n = 65) assessed plantar responses of two to four different patients. Their judgment was compared with that of one senior neurologist. Only the students who had seen the videotape showed a significant improvement in performance on a second test (t-test, t = -2.26, p = 0.031). In addition, these students more frequently took account of the flexion synergy (Fisher exact test, p less than 0.001). Video can be an efficient tool in medical education.     

Donor interleukin-4 promoter gene polymorphism influences allograft rejection after heart transplantation.

BACKGROUND: The cytokine interleukin-4 (IL-4) is secreted mainly by activated T lymphocytes and characterizes the T-helper 2 (Th2) sub-type. In transplantation Th2 cells are believed to induce graft tolerance. Previous studies revealed that patients with a relatively high frequency of IL-4 producing helper T lymphocytes (HTL) before heart transplantation (HTX) had no or less rejection episodes compared with patients with a low frequency of IL-4 producing HTL. Three single nucleotide polymorphisms (SNPs) have been identified in the promoter region of the IL-4 gene, which influence promoter strength. We investigated whether there was a correlation between SNP genotypes in the IL-4 promoter and heart failure, and rejection after HTX. METHODS: Seventy HTX patients, 61 donors, and 36 controls were genotyped for the 3 SNPs by sequencing. RESULTS: Of the SNPs at -285 and -81, only the C and A alleles, respectively, were found in this study. Both alleles were found for the -590 SNP. No relation between patient genotype of the SNP at -590 and heart failure and rejection was found. However, incidence of rejection was significantly lower in patients that received a donor heart with the T-positive genotype compared with patients that received a heart from a T-negative donor. Patients who had the T-negative genotype and received a heart from a T-positive donor, suffered significantly less from rejection than T-negative patients that received a T-negative donor heart. This was not significant in the T-positive patient group. CONCLUSIONS: This indicates that IL-4 production within the donor heart and by cells from the donor is important for reducing incidence of episodes of rejection.     

Detection of optic pathway misrouting in the human albino neonate.

The diagnosis of albinism is indicated by the presence of visual pathway misrouting in which temporal retinal fibers erroneously decussate at the optic chiasm disrupting the normal topographical distribution of retinal geniculate-cortical projections. Detection of misrouted fibers is effected by non-invasive electrophysiological assessment of the topographical representation of the visual evoked potential (VEP) following full field monocular stimulation. By combining appropriate state defined neonatal recording procedures with the albino VEP test paradigm, the presence of aberrant optic pathway projections was detected in a five-day-old full-term infant. The electrophysiological signature pathognomonic to albinism was observed within a long (300 ms) latency window of an otherwise normal neonatal luminance flash response. The results of this study indicate that the VEP misrouting test can be extended to reliable albino diagnosis within the neonatal period.     

Studies on the contact system of coagulation during therapy with high doses of recombinant IL-2: implications for septic shock

Patients treated with high doses of interleukin-2 (IL-2) because of cancer, develop hemodynamic and vasopermeability changes, that resemble those observed in sepsis. These patients thus provide a unique opportunity to study the early events in the development of septic shock. We analysed the changes that occurred in the contact system of coagulation in plasma from 4 patients, who together received seven 12-day cycles of high doses of IL-2. Levels of factor XII and prekallikrein during the cycles progressively fell to 50 and 30% of their initial levels, respectively, whereas significant increases in plasma factor XIIa- and kallikrein-C1-inhibitor complexes were not observed (in 3 out of 211 samples slightly increased levels of both complexes were found). The reductions in factor XII and prekallikrein were only in part due to protein leakage, since levels were still significantly lower, i.e., 80 and 50%, respectively, when corrected for albumin decreases. Levels of high molecular weight kininogen (HMWK) also decreased during IL-2 therapy, however, this decrease paralleled that of albumin. SDS-PAGE analysis of plasma HMWK did not reveal increased cleavage of this protein. The reduction of factor XII and prekallikrein, corrected for protein leakage, significantly correlated with albumin levels and inversely with daily cumulative weight gain in the patients. Thus, we demonstrate that factor XII and prekallikrein decrease during IL-2 therapy. As these decreases, already observed after 1 day treatment, were disproportional to that of albumin, a negative acute phase reactant, and correlated with signs of the vascular leak syndrome, we favor the explanation that they reflected activation rather than a decreased synthesis of the contact system proteins.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reduced graft-versus-host disease-inducing capacity of T cells after activation, culturing, and magnetic cell sorting selection in an allogeneic bone marrow transplantation model in rats.

Graft-versus-host disease (GvHD), a major complication of allogeneic bone marrow transplantation, has been ascribed to mature T cells in the graft. Because T cells play an important role in engraftment of the bone marrow and decrease the probability of relapse of leukemia, a treatment strategy was developed to preserve the benefits of T cells in the graft and to control the severe complications of GvHD. This can be accomplished by the genetic modification of donor T cells with a suicide gene that allows their selective in vivo elimination and subsequently the abrogation of GvHD. For clinical benefit the alloreactivity of herpes simplex virus thymidine kinase (HSV-TK) gene-transduced T cells should be retained. Therefore, we investigated the influence of gene transduction and the selection procedure on T cells. We demonstrated that activation and culturing of T cells reduce their capacity to induce lethal GvHD in an allogeneic rat bone marrow transplantation model. Furthermore, positive immunomagnetic selection of gene-transduced T cells resulted in loss of the GvHD-inducing capacity of HSV-TK(+) T cells directly after MACS (magnetic cell sorting) selection; this loss could be recovered by a 1-day expansion of the selected T cells. No effect on alloreactivity was observed to be caused by the gene transduction procedure. Our study resulted in the development of an optimized culture and gene transduction protocol with preservation of T cell alloreactivity. Treatment of transplanted rats with ganciclovir resulted in a rapid reduction in the number of HSV-TK(+) T cells in the peripheral blood and in increased survival of the animals.