Interferon-alpha induces circulating tumor necrosis factor receptor p55 in humans

In the present studies we investigated the effect of interferon-alpha (IFN alpha) on the release of the soluble (extracellular) form of the tumor necrosis factor p55 receptor (TNFsRp55), because TNFsRp55 is a natural antagonist of tumor necrosis factor (TNF)-induced inflammation and also might be part of the antiinflammatory properties of IFN alpha. Plasma levels of TNFsRp55 were measured by a specific radioimmunoassay in five healthy volunteers and in five patients with chronic hepatitis C treated with IFN alpha. Levels showed a significant increase after a single injection of 5.0 million U IFN alpha in both healthy and hepatitis patient groups. Peak values (3.5 to 4.5 ng/mL) were observed within 12 hours of beginning treatment. Thereafter, levels promptly declined, reaching baseline values within 24 hours. TNF alpha and C- reactive protein (CRP) levels were below the detection limit in the same plasma samples. In addition, IFN alpha suppressed significantly interleukin (IL)-1 alpha-induced TNF alpha protein synthesis by human peripheral blood mononuclear cells. These results suggest that the antiinflammatory properties of IFN alpha may be, in part, also due to the induction and/or release of TNF soluble receptors and the suppression of TNF alpha synthesis.     

IgE-independent interleukin-4 expression and induction of a late phase of leukotriene C4 formation in human blood basophils

T-helper cells can differentiate into at least two subtypes secreting distinct profiles of cytokines, Th1 and Th2, regulating immunoprotection and different immunopathologies. Interleukin-4 (IL-4) is both the product and the inducer of Th2 cells, raising the question whether IL-4 can be produced in response to antigen-independent stimuli. Here we show that human basophils produce IL-4 on stimulation with IL-3 and C5a or C5adesarg in similar amounts as induced by IgE- receptor-cross-linking. C5a-induced IL-4 production requires the presence of IL-3, with little effect of the sequence of stimuli addition. No "Th1-cytokines" (interferon-gamma and IL-2) and even no "Th2-cytokines" (IL-3, IL-5, IL-10, and granulocyte-macrophage colony- stimulating factor) are produced by basophils in response to either IgE- dependent or IgE-independent activation. The generation of leukotriene C4 (LTC4) is regulated in a similar manner. However, C5a induces a rapid, transient burst of leukotriene formation only if added after IL- 3. Interestingly, upon prolonged culture, a late phase of continuous LTC4 production is observed, which also requires two signals (IL-3 and C5a), but rather depends on their continuous presence than on their sequence of action. These data describe an antigen-independent pathway of very restricted IL-4 expression. Thus, basophils must be considered as central immunoregulatory cells of the innate immune system. Furthermore, the results show that LTC4 can also be generated more continuously for many hours, a phenomenon that may be of particular importance in chornic allergic inflammation, such as asthma.     

Fetal hemoglobin induction by acetate, a product of butyrate catabolism [see comments]

Butyrate induces fetal hemoglobin (HbF) synthesis in cultures of erythroid progenitors, in primates, and in man. The mechanism by which this compound stimulates gamma-globin synthesis is unknown. In the course of butyrate catabolism, beta oxidation by mitochondrial enzymes results in the formation of two acetate molecules from each molecule of butyrate. Studies were performed to determine whether acetate itself induces HbF synthesis. In erythroid burst-forming unit (BFU-E) cultures from normal persons, and individuals with sickle cell disease and umbilical-cord blood, dose-dependent increases in gamma-globin protein and gamma mRNA were consistently observed in response to increasing acetate concentrations. In BFU-E cultures from normal adults and patients with sickle cell disease, the ratio of gamma/gamma + beta mRNA increased twofold to fivefold in response to acetate, whereas the percentage of BFU-E progeny staining with an anti-gamma monoclonal antibody (MoAb) increased approximately twofold. Acetate-induced increases in gamma-gene expression were also noted in the progeny of umbilical cord blood BFU-E, although the magnitude of change in response to acetate was less because of a higher baseline of gamma- chain production. The effect of acetate on HbF induction in vivo was evaluated using transgenic mouse and primate models. A transgenic mouse bearing a 2.5-kb mu locus control region (mu LCR) cassette linked to a 3.3-kb A gamma gene displayed a near twofold increase in gamma mRNA during a 10-day infusion of sodium acetate at a dose of 1.5 g/kg/d. Sodium acetate administration in baboons, in doses ranging from 1.5 to 6 g/kg/d by continuous intravenous infusion, also resulted in the stimulation of gamma-globin synthesis, with the percentage of HbF- containing reticulocytes (F reticulocytes) approaching 30%. Surprisingly, a dose-response effect of acetate on HbF induction was not observed in the baboons, and HbF induction was not sustained with prolonged acetate administration. These results suggest that both two- carbon fatty acids (acetate) and four-carbon fatty acids (butyrate) stimulate synthesis of HbF in vivo.     

Clonality in juvenile chronic myelogenous leukemia

Juvenile chronic myelogenous leukemia (JCML) is a myeloproliferative disease in which morbidity and mortality are primarily caused by nonhematopoietic organ failure from myelomonocytic infiltration or by failure of the normal bone marrow. Morphologic evidence of maturation arrest, karyotypic abnormalities, and progression to blast crisis are infrequent events. Viral infections and other reactive processes can initially mimic the clinical course of JCML, creating diagnostic problems. Because of the rarity of JCML and technical limitations, formal clonality studies have not been reported previously. Nine female JCML patients were identified by clinical criteria, characteristic 'spontaneous' in vitro cell growth, and negative cultures and titers for various viral agents. Peripheral blood and bone marrow samples were obtained at the time of diagnosis for cell separation and RNA and DNA isolation. To assess clonality, X-chromosome inactivation patterns were evaluated using three different, recently developed polymerase chain reaction-based clonality assays. All nine female JCML patients showed evidence for monoclonal origin of mononuclear cells at the time of diagnosis. Cell separation studies further traced the monoclonal origin back to at least the most primitive myeloid progenitor cell. Reversion to a polyclonal state was demonstrated after bone marrow transplant and also in one patient following treatment with 13-cis retinoic acid. This demonstration of clonality in JCML delineates it from the reactive processes and provides a basis for molecular genetic strategies to identify causally associated mutations.     

Studies on the interaction between GP-18-0-deficient neutrophils and vascular endothelium

A patient whose neutrophils lack the glycoprotein gp-180 shows an increased susceptibility to bacterial infections. Neutrophils from this patient migrate abnormally both in vivo and in vitro. To examine the basis for this abnormality in migration, a study was carried out on the interaction of gp-180-deficient neutrophils with artificial surfaces and with human endothelial cell cultures. Compared with normal neutrophils. gp-180-deficient neutrophils showed decreased adhesion to cold-insoluble globulin-coated plastic surfaces, and their ability to spread on this substratum was greatly impaired. In contrast, gp-180- deficient neutrophils interacted in a normal fashion with endothelial monolayers, attaching to their surfaces and migrating between cell junctions to spread between the monolayers and the subjacent plastic. A normal interaction with endothelium in vivo was implied by the finding that the rise in the neutrophil count in response to epinephrine, an index of the marginated pool, was normal in the gp-180-deficient patient. We conclude that the abnormal function of gp-180-deficient cells is unlikely to be caused by a faulty interaction with the vascular endothelium. We postulate instead that these cells migrate poorly in vivo because of an abnormal interaction with extravascular connective tissue matrix constituents.     

A combination of the effects of rare genotypes at the XK and KEL blood group loci results in absence of Kell system antigens from the red blood cells

The 22 antigens of the Kell blood group system are located on a red blood cell (RBC) membrane glycoprotein that shows sequence homology with a family of metalloendopeptidases. Expression of the Kell system antigens is partially governed by XK, an X-linked gene that encodes the Kx protein; absence of Kx results in reduced Kell antigen expression. Almost total absence of Kell antigens from the RBCs of a German man with no symptoms of neuroacanthocytosis could not be due to the Kell- null phenotype, Ko, because his RBCs had very weak expression of Kx antigen and his three children were Kp(a + b+). Kell antigens were normal on the RBCs of his son but weak on those of his two daughters. An Nla III restriction fragment-length polymorphism within the KEL gene showed the Kpa/Kpa genotype in the propositus. Sequencing of his XK gene showed a single base change within the donor splice consensus sequence of intron 2. A BsaAl restriction fragment-length polymorphism showed the mutation in both of his daughters but not in his son. The extreme depression of the Kell antigens of the propositus must be due to a combination of effects, ie, homozygosity for Kpa and deficiency of Kx protein, each of which is capable of causing some degree of weakening of Kell antigens.