Model of Epstein-Barr virus infection of human thymocytes: expression of viral genome and impact on cellular receptor expression in the T- lymphoblastic cell line, HPB-ALL

Infection of B lymphocytes and epithelial tissue by Epstein-Barr virus (EBV) is associated with malignancy and autoimmunity. The cellular receptor for EBV has been identified as CD21 (CR2). A molecule, which is biochemically and immunologically similar to B-cell CD21, has been identified on a subpopulation of immature thymocytes, suggesting a role for this molecule in the regulation of T-cell development and further suggesting that immature T cells might be susceptible to EBV infection. A growing body of literature now documents the presence of EBV in tumors of T-cell origin. We have evaluated the susceptibility of the human immature T cell line, HPB-ALL, to infection by EBV. Electron microscopy studies showed a rapid internalization of virus by HPB cells. Southern blotting showed the intracellular presence of linear EBV genomes, and components of the virus replicative cycle were identified. Expression of the BamHI Z region of the genome, encoding the nuclear protein, ZEBRA, which is strictly associated with productive infection in B cells, was detected in HPB-ALL cells. A spliced variant of Z, RAZ, was also identified. Cell surface expression of EBV late antigens was observed to occur transiently. Infection of HPB cells was also accompanied by altered expression of T-cell surface molecules involved in antigen recognition, a process critical to normal development of the T-cell repertoire. Delineation of the outcome of T- cell infection by EBV may lead to a better understanding of the role of this virus in autoimmune processes and malignancy.     

PreCimp: Pre‐collapsing imputation approach increases imputation accuracy of rare variants in terms of collapsed variables

Imputation is widely used for obtaining information about rare variants. However, one issue concerning imputation is the low accuracy of imputed rare variants as the inaccurate imputed rare variants may distort the results of region‐based association tests. Therefore, we developed a pre‐collapsing imputation method (PreCimp) to improve the accuracy of imputation by using collapsed variables. Briefly, collapsed variables are generated using rare variants in the reference panel, and a new reference panel is constructed by inserting pre‐collapsed variables into the original reference panel. Following imputation analysis provides the imputed genotypes of the collapsed variables. We demonstrated the performance of PreCimp on 5,349 genotyped samples using a Korean population specific reference panel including 848 samples of exome sequencing, Affymetrix 5.0, and exome chip. PreCimp outperformed a traditional post‐collapsing method that collapses imputed variants after single rare variant imputation analysis. Compared with the results of post‐collapsing method, PreCimp approach was shown to relatively increase imputation accuracy about 3.4–6.3% when dosage r² is between 0.6 and 0.8, 10.9–16.1% when dosage r² is between 0.4 and 0.6, and 21.4 ～ 129.4% when dosage r² is below 0.4.     

Soluble kit receptor in human serum

c-kit encodes the transmembrane receptor tyrosine kinase (Kit) for the recently described ligand stem cell factor (SCF). We have developed an enzyme-linked immunosorbent assay for measuring soluble human Kit and we have used the assay to show high levels of soluble Kit in human serum. The distribution of soluble Kit levels was investigated among 112 normal human serum donors. The mean serum level (+/- SD) was found to be 324 +/- 105 ng/mL with the values falling between 163 ng/mL and 788 ng/mL. No correlation between soluble Kit levels and the sexes or ages of the donors was found. Partial purification using immunoaffinity chromatography allowed us to characterize the soluble Kit from pooled human serum. Antibodies generated to a 497-amino acid recombinant human soluble Kit corresponding to the N-terminal extracellular domain of the receptor recognized the serum-derived soluble Kit by immunoblotting. We found that the serum-derived soluble Kit is glycosylated, with mostly N- linked but also O-linked carbohydrate, and with terminal sialic acid residues. When compared with the recombinant human soluble Kit, the serum-derived material was similar both in size and glycosylation pattern. CNBr cleavage of the isolated serum-derived material followed by amino terminal sequencing confirmed the presence of five peptides expected for the extracellular portion of the Kit molecule. The immunoaffinity purified serum-derived soluble Kit inhibited binding of [125I]SCF to membrane-bound receptor in an in vitro assay. These results indicate that soluble Kit could modulate the activity and functions of SCF in vivo.     

Serum interleukin-3 levels following autologous or allogeneic bone marrow transplantation: effects of T-cell depletion, blood stem cell infusion, and hematopoietic growth factor treatment

Engraftment of marrow following autologous or allogeneic bone marrow transplantation (BMT) may be influenced by quantity and function of stem cells. T lymphocytes, supporting microenvironmental cells, and hematopoietic growth factors (HGF). To elucidate the physiologic role of interleukin-3 (IL-3) in the engraftment process, serum IL-3 levels were measured in over 400 samples from 77 transplant recipients before and for up to 3 weeks following transplantation using a novel enzyme- linked immunoabsorbent assay (ELISA) with a sensitivity of > or = 78 pg/mL. Thirty-seven patients received two to three log T-cell-depleted allografts. In the remaining 40 patients (18 autologous marrow, 12 allogeneic marrow, and 10 autologous peripheral blood [PB] stem cell), T cells were not depleted (non-TCD) from the grafts. A burst of IL-3 (peak levels, 1,500 to 6,000 pg/mL) was detected in the immediate posttransplant period between day 0 and day 14 in all non-TCD recipients and in 21 of 37 (57%) of TCD recipients. A strong inverse relationship between IL-3 levels and absolute neutrophil count (ANC) was observed in both non-TCD recipients (r = -.796) and in TCD recipients (r = -.897). However, both peak IL-3 levels and mean IL-3 levels from day 0 through 14 were significantly lower in TCD recipients compared with either autologous or unmodified allogeneic marrow recipients (P < .01). The lowest peak or mean day 0 through 14 IL-3 levels were observed in matched related recipients undergoing the most aggressive (2.5 to 3.0 log) T-cell-depleted BMT. Autografted patients receiving blood stem cell transplants alone or posttransplant granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony stimulating factor (GM-CSF) also had significantly lower peak IL- 3 levels (P < .01). In patients receiving TCD grafts, administration of antithymocyte globulin (ATG) posttransplant significantly increased peak IL-3 levels compared with patients not treated with ATG (P < .04). This study shows that endogenous release of IL-3 is strongly associated with myeloid engraftment and inversely related to ANC. Removal of T lymphocytes from donor marrow or acceleration of engraftment by use of stem cells or growth factors appears to blunt the endogenous release of IL-3 whereas use of ATG posttransplant increases IL-3 release.     

Kernicterus in an adult who is heterozygous for Crigler-Najjar syndrome and homozygous for Gilbert-type genetic defect

Gilbert syndrome is a common genetic disorder associated with mild unconjugated hyperbilirubinemia and no clinical illness. In contrast, Crigler-Najjar syndrome types I and II are rare genetic disorders associated with severe unconjugated hyperbilirubinemia and a life-long risk of kernicterus. Patients with Gilbert syndrome have low levels of a normal form of uridinediphosphoglucuronate glucuronosyltransferase because of a defect in the promoter region of both alleles, whereas patients with Crigler-Najjar syndrome are homozygous for a defect that yields an abnormal form of the enzyme that has limited or no activity. This case report describes a young adult with Crigler-Najjar syndrome type II in whom kernicterus developed after a laparoscopic cholecystectomy. The development of kernicterus was the result of a largely preventable series of events that lead to an increase in the free fraction of his serum bilirubin. Analysis of his genetic defect showed that he was homozygous for the mutation associated with Gilbert syndrome and heterozygous for a second mutation in the open reading frame of one allele of the bilirubin uridinediphosphoglucuronate glucuronosyltransferase gene. The combined defect leads to severe hyperbilirubinemia and shows how seemingly benign genetic defects, when combined, can cause serious clinical disease. (Gastroenterology 1997 Jun;112(6):2099-103)     

Shear-induced platelet aggregation requires von Willebrand factor and platelet membrane glycoproteins Ib and IIb-IIIa

Different types of platelets in various types of plasma were subjected to levels of shear stress that produce irreversible platelet aggregation in normal platelet-rich plasma (PRP). At shear stresses of 90 or 180 dyne/cm2 applied for 30 seconds or five minutes, aggregation was either absent or only transient and reversible using severe von Willebrand's disease (vWD) PRP (less than 1% von Willebrand factor, vWF); Bernard-Soulier syndrome (BSS) PRP (platelets deficient in the membrane glycoprotein Ib, GPIb); normal PRP plus monoclonal antibody (MoAb) to GPIb; thrombasthenic PRP (platelets deficient in membrane glycoprotein IIb-IIIa complex, GPIIb-IIIa); and normal PRP plus MoAb to GPIIb-IIIa. Shear-induced aggregation was inhibited under the above conditions, even though the platelets were activated to release their granular contents. Sheared normal platelets in vWD plasma aggregated in response to added vWF. These studies demonstrate that the formation of stable platelet aggregates under conditions of high shear requires vWF and the availability of both GPIb and GPIIb-IIIa on platelet membranes. The experiments demonstrate that vWF-platelet interactions can occur in the absence of artificial agonists or chemical modification of vWF. They suggest a possible mechanism for platelet aggregation in stenosed or partially obstructed arterial vessels in which the platelets are subjected to relatively high levels of shear stress.     

Modulation of polymorphonuclear leukocyte function by cetiedil

Cetiedil citrate monohydrate inhibits sickling of red cells and aggregation of platelets. We assessed its ability to attenuate polymorphonuclear leukocyte (PMN) function. PMN aggregation in response to 2 X 10(-7) M formyl-met-leu-phe (FMLP) was inhibited in a dose- dependent fashion by cetiedil concentrations ranging from 60 to 250 microM. Additionally, 125 microM cetiedil inhibited PMN aggregation in response to 2 X 10(-7) M FMLP, 20 ng/ml phorbol myristate acetate (PMA), and 1 X 10(-6) M A23187 by 69% +/- 18%, 72% +/- 20%, and 65% +/- 4%, respectively. Inhibition of FMLP-induced aggregation was provided by only 5 min of incubation of the drug with the cells and was partially reversible. Cell viability was unaffected by exposure of PMN to the drug. Correspondingly, 125 microM cetiedil prevented the translocation of calcium from the PMN membrane as assessed by chlorotetracycline fluorescence. Paralleling the effect of the drug on PMN aggregation, 125 microM cetiedil inhibited release of superoxide by 55% and decreased the number of available 3H-FMLP receptors. However, its effect on release of the primary granule constituent, myeloperoxidase, was minimal (4.5% inhibition), while the effect on release of the specific granule product, lactoferrin (27% inhibition), was modest. These studies indicate that cetiedil affects PMN aggregation and superoxide release to a much greater extent than PMN degranulation. Thus, cetiedil may have potential uses in modulating inflammatory response in vivo.     

Increased soluble interleukin-1 type II receptor concentrations in postoperative patients and in patients with sepsis syndrome

Plasma interleukin-1 (IL-1) activity is modulated in part through the simultaneous appearance of several inhibitors of IL-1 action, including interleukin-1 receptor antagonist (IL-1ra) and the soluble IL-1 type II receptor (IL-1RII). However, little is known concerning the plasma appearance of these inhibitors in patients following operative trauma or those with sepsis syndrome. In the present report, plasma IL-1beta, IL-1ra, and soluble IL-1RI and IL-1RII concentrations were evaluated in 118 patients with sepsis syndrome or after elective operative trauma. Plasma concentrations of IL-1ra increased significantly following elective operative repair of thoraco-abdominal and abdominal aortic aneurysms, and after bowel resection for inflammatory bowel disease, but did not increase after laparoscopic cholecystectomy. Plasma IL-1ra levels were also elevated in patients with sepsis syndrome. In contrast, soluble IL-1RII levels were only increased in patients after operative repair of thoraco-abdominal aortic aneurysms and in sepsis syndrome, whereas concentrations were unaffected by the other more modest surgical procedures. Plasma IL-1RI concentrations decreased in all postoperative patients in the first 24 hours after surgery. We conclude that both plasma IL-1ra and soluble IL-1RII concentrations often increase in sepsis and following some operative trauma. Less severe operative trauma increases the plasma concentration of only IL- 1ra, whereas both IL-1ra and soluble IL-1RII are increased in patients with sepsis syndrome or following thoraco-abdominal aneurysm repair.