Functional characterization of the human interleukin-15 receptor alpha chain and close linkage of IL15RA and IL2RA genes.

Interleukins-2 and -15 (IL-2 and IL-15) are cytokines with overlapping but distinct biological effects. Their receptors share two subunits (the IL-2R beta and -gamma chains) that are essential for signal transduction. The IL-2 receptor requires an additional IL-2-specific alpha subunit for high affinity IL-2 binding.

Translational control of globin chain ontogeny in hamster yolk sac erythroid cells.

Prior research has demonstrated that globin ontogeny of hamster proceeds nearly to completion during the several days that yolk sac erythroid cells (YSEC) circulate in the embryo; synthesis of embryonic globin chains gives way to synthesis of adult globin chains in these primitive cells. In the present study, we translated total cell RNA extracted from YSEC on days 9-13 of gestation in wheat germ cell-free extract, expecting to observe the same progressive rise that occurs in vivo in rates of translation of alpha- and beta-globin mRNA during ontogeny. The opposite occurred; translation rates of both globins decreased sharply.

Erythropoietin. Receptor characteristics during the ontogeny of hamster yolk sac erythroid cells.

Erythropoietin (Epo) binds specifically to receptors on the surface membrane of responsive erythroid cells. In search of ontogenic changes in Epo receptor behavior, we studied characteristics of specific binding to hamster yolk sac erythroid cells during hamster ontogeny. We detected receptors specific for Epo on these cells throughout the duration of their intravascular existence (hamster gestational days 8 through 13).

The globin gene expression program in the hamster embryo.

Molecular mechanisms involved in control of globin gene expression are a prominent target in current basic biologic research. A better understanding of these mechanisms might also impinge on a clinical goal: amelioration of the human hemoglobinopathies. Recent reports have established the coexistence of embryonic and adult globins in rodent yolk-sac erythroid cells, raising the possibility that globin ontogeny takes place in these cells.

Ontogeny of hamster hemoglobins in yolk-sac erythroid cells in vivo and in culture.

During mammalian hemoglobin ontogeny, synthesis of the earliest globin chains (embryonic) is ultimately replaced by synthesis of globin chains (adult) characteristic of the fully formed organism. Elements of control of initiation, progression, and completion of globin-chain ontogeny are poorly understood. In search of a cell culture system in which ontogeny might be studied under closely controlled experimental conditions, we chose erythroid cells of the hamster embryo.

Studies on globin chain synthesis during hamster development.

Erythroid cells derived from the yolk-sac of the hamster embryos replicate in the embryonic circulation, actively synthesize hemoglobin, and are the dominant circulating erythroid cell through day 14 of gestation. Until day 11, at which time fetal liver rudiments appear, they are the only erythroid tissue present in the embryo. Because of their size (Fig.

Characteristics of I and i antigen receptors on the membrane of erythrocytes in sickle cell anemia.

In this study we employed two approaches in attempts to explain the increased expression of I and i antigens on the membrane surface of SS erythrocytes: immunoelectron microscopy and measurements of antigen-antibody affinity. AA and SS erythrocytes were first reacted with anti-I or anti-i antisera, and then with ferritin-conjugated anti-human IgM. With both antibodies, proportions of cells labeled and ferritin-cluster density on labeled cells were greater for SS erythrocytes at a high level of significance.

Simultaneous expression of globin genes for embryonic and adult hemoglobins during mammalian ontogeny.

The dominant hemoglobin of the adult hamster was detected in yolk-sac erythroid cells, and its identity was confirmed by peptide mapping and by analysis of relevant peptides. Both the presence and active synthesis of two embryonic hemoglobins presumed to exist only in yolk-sac erythroid cells were detected in neonatal liver and spleen. Thus the time span of expression of both embryonic and adult globin genes during mammalian ontogeny may be considerably broader than presently believed.

Role of membrane lipids in cold agglutination of human erythrocytes.

The membrane lipid fluidity of normal human erythrocytes was modified by enrichment and depletion in cholesterol, and the expression of I and SP1 antigens was assayed by quantitative hemagglutination from 4 degrees to 24 degrees C by use of a continuous flow system. Below 16 degrees--18 degrees C, cholesterol enrichment increased and cholesterol depletion decreased percent agglutination. As temperatures approached approximately 18 degrees--20 degrees C, differences in agglutination between modified and unmodified erythrocytes became insignificant despite marked differences in lipid fluidity at that temperature.

Variability of intracellular pH within individual populations of SS and AA erythrocytes.

Individual populations of AA and SS erythrocytes were fractionated according to cell density by centrifugation, and the fractions analysed for intracellular pH (PHi), the mole ratio of 2,3-diphosphoglycerate to haemoglobin (DPG:Hb), and cell concentration of haemoglobin (MCHC). The pHi of SS erythrocytes was consistently lower than that of AA erythrocytes throughout the density range, and the lowest pHi of both cell types (AA and SS) was found in cells with the highest density. As the highest density AA and SS erythrocytes are characterized by the lowest DPG:Hb values, their relatively low pHi cannot be ascribed to intracellular organic phosphate.

Fetal characteristics of erythrocytes in sickle cell anemia: an immunofluorescence study of individual cells.

In a group of disease states that includes sickle cell anemia (SS disease), two fetal erythrocyte markers, Hb F and i antigen, persist into adulthood. Using the technique of single-cell immunofluorescence, we determined the expression of l-i antigens and the presence of Hb F within populations of erythrocytes. Subjects tested included normal adults, normal newborns, patients with SS disease, and individuals with sickle cell trait.

Increased expression in erythrocytic Ii antigens in sickle cell disease and sickle cell trait.

The reactivity of human erythrocytes with anti-I and anti-i sera was estimated in 36 normal adults, 18 individuals with sickle cell anemia and 27 individuals with sickle cell trait, by quantitative hemagglutination with a sensitive autoanalyzer system. SS erythrocytes showed significantly increased I and i reactivity when compared to normal erythrocytes. AS erythrocytes also demonstrated some increase in Ii reactivity.

Effect of 2, 3-diphosphoglycerate on the solubility of deoxy-sickle hemoglobin.

We have examined the effect of 2, 3-diphosphoglycerate (DPG) on the solubility of deoxy-sickle hemoglobin (deoxy-Hb S) under conditions such that concentration, pH, and osmolarity of deoxy-Hb S solutions approached physiological. The range of DPG/Hb molar ratios encompassed the extremes found for this ratio in erythrocytes from individuals with sickle cell anemia. After monomer-polyer equilibrium had been established, the phases were separated by centrifugation and assayed for concentrations of Hb and DPG.

Intermolecular interactions of oxygenated sickle hemoglobin molecules in cells and cell-free solutions.

We have measured the intermolecular interactions of oxygenated sickle hemoglobin molecules in cells and in cell-free solutions, and have compared the results with similar data for liganded normal adult hemoglobin. The experiments involve the measurement of the spin-lattice relaxation time T1 of protons of solvent water molecules, as a function of an externally applied static magnetic field. From such data, one can derive a correlation time tauc, for each sample, which is a measure of the time taken for a hemoglobin molecule to randomize its orientation due to Brownian motion.

Thermodynamic studies of polymerization of deoxygenated sickle cell hemoglobin.

Solubilities of deoxygenated sickle cell hemoglobin (deoxy-Hb S), at varying pH and temperature over a range of concentrations encompassing those found in erythrocytes, were measured. The technique involved ultracentrifugation, which gave values of the supernatant concentration and the mass of the sedimented material. The data establish that the solubility of doexy-Hb S is the saturation concentration and is independent of initial concentration.