Identification of glycoprotein Ib as a target for autoantibody in idiopathic (autoimmune) thrombocytopenic purpura

An antibody (DIL) from a patient with idiopathic thrombocytopenic purpura (ITP) was shown to have autospecificity on the basis of reactions with autologous platelets that were identical to those obtained with platelets from normal subjects. DIL antibody also reacted strongly in an immunofluorescence test with platelets from a patient with Glanzmann's thrombasthenia, but failed to react with platelets from a patient with the Bernard-Soulier syndrome who was known to be deficient in glycoprotein Ib (GPIb). Purified GPIb and control platelets, but not Bernard-Soulier platelets, inhibited the lytic activity of DIL. Using the GPIb-specific monoclonal antibody AP1 and one-dimensional rocket electrophoresis into gels containing rabbit antihuman platelet membrane antibody, it was shown that staphylococcal protein A-Sepharose beads coated with DIL antibody selectively remove GPIb from solubilized platelet preparations. By crossed immunoelectrophoresis it was found that DIL recognizes a determinant on GPIb on the membrane side of the cleavage site of the platelet calcium- activated protease (calpain). These studies provide direct evidence for binding of a platelet autoantibody to a determinant on GPIb relatively close to the site of insertion of this protein into the platelet membrane.     

Invasion of erythrocytes by Plasmodium falciparum malaria parasites: evidence for receptor heterogeneity and two receptors

Plasmodium falciparum malaria parasites with different capabilities of invading sialic acid-deficient erythrocytes were identified. Thai-2 parasites cultured in Tn erythrocytes invaded neuraminidase-treated and Tn erythrocytes twice as efficiently as Thai-2 parasites cultured in normal erythrocytes and seven to ten times more efficiently than a cloned line of Camp parasites cultured in normal erythrocytes. All three parasite lines required sialic acid for optimal invasion, but Thai-2 parasites cultured in Tn erythrocytes invaded neuraminidase- treated erythrocytes with 45% efficiency whereas Camp parasites invaded neuraminidase-treated erythrocytes with less than 10% efficiency. P falciparum malaria parasites probably possess two receptors: one that binds to a sialic acid-dependent ligand and another that binds to a sialic acid-independent ligand. Parasites may differ in the quantity or affinity of their receptors for the sialic acid-independent ligand.     

Differential coupling of CC chemokine receptors to multiple heterotrimeric G proteins in human interleukin-2-activated natural killer cells

Using two different approaches, we have investigated the types of G proteins coupled to CC chemokine receptors. First, permeabilization of interleukin-2-activated natural killer (IANK) cells with streptolysin-O and introduction of anti-G protein antibodies inside these cells resulted in the following. (1) Anti-G(s), anti-G(o), and anti-G(z) inhibited the migration of IANK cells in response to macrophage- inflammatory protein-1 alpha (MIP-1 alpha), monocyte chemoattractant protein-1 (MCP-1), or regulated on activation normal T cell expressed and secreted (RANTES). (2) Anti-Gi inhibited their migration in response to MCP-1 or RANTES but not in response to MIP-1 alpha. Second, incubation of IANK cell membranes with anti-G protein antibodies before incubating with (gamma-35S) GTP or (gamma-32P) GTP, resulted in the following. (1) Anti-G(s), anti-G(o), or anti-G(z) inhibited GTP binding and GTPase activity in the presence of MIP-1 alpha, or RANTES. (2) Anti- G(i) inhibited GTP binding and GTPase activity in the presence of MCP-1 or RANTES but not in the presence of MIP-1 alpha. The inhibitory effect of anti-G protein antibodies was reversed upon incubating these antibodies with their respective synthetic peptides before addition to IANK cell membranes. These results suggest that MCP-1 and RANTES receptors are promiscuously coupled to multiple G proteins in IANK cell membranes and that this coupling is different from MIP-1 alpha receptors, which seem to be coupled to G(s), G(o), and G(z) but not to G(i).     

Improved red blood cell preservation correlates with decreased loss of bands 3, 4.1, acetylcholinestrase, and lipids in microvesicles

In earlier studies we have shown that a final concentration of 0.69% glycerol in blood mixed with an experimental additive solution, EAS 25, improves the in vitro quality and in vivo survival of red blood cells (RBCs). The objective of this study was to determine if the better preservation of RBCs in EAS 25 is correlated with the improved maintenance of membrane lipids and proteins and decreased vesiculation. Split units of RBCs were stored in Adsol or EAS 25 (mmol/L: adenine 2/2, dextrose 122/110, mannitol 42/55, glycerol 0/150, NaCl 154/50). After 12 weeks storage, RBC and microvesicle membranes were analyzed for cholesterol, phospholipid, diphenyl hexatriene fluorescence anisotropy, and acetylcholinesterase (AchE) activity. Bands 3 and 4.1 were identified in the microvesicle membranes by immunoblotting. The RBC membrane cholesterol, phospholipids, and AchE remained higher in EAS 25 than in Adsol (P < .001). Vesicle membrane lipids and AchE in EAS 25 were significantly less than in Adsol (P < .001). The fluidity of stored cells in both the solutions was greater than the prestorage samples. Immunoblotting analyses showed that bands 3 and 4.1 were greatly reduced in the microvesicle membranes shed by the RBCs stored in EAS 25 compared with those formed in Adsol.     

Independent regulation of M-CSF and G-CSF gene expression in human monocytes

The macrophage and granulocyte colony-stimulating factors, M-CSF and G- CSF, act in vitro to induce proliferation and differentiation of monocyte and granulocyte progenitor cells, respectively. We show here that both of these CSFs can be produced by stimulated human blood monocytes, but the M-CSF and G-CSF genes are independently regulated. Recombinant human interleukin-3 (IL-3) and GM-CSF primarily induce expression of the M-CSF gene and secretion of M-CSF, whereas bacterial lipopolysaccharide primarily induces expression of the G-CSF gene and secretion of G-CSF. These results suggest that under different conditions of in vitro stimulation the monocyte secretes factors that could lead selectively to either granulocyte or monocyte production.     

Identification of a second transforming gene, rasn, in a human multiple myeloma line with a rearranged c-myc allele

Multiple myeloma is a disease characterized by a long, slowly progressive phase and a final, more aggressive one. Little is known about the mechanism of transformation of myeloma cells, although the clinical characteristics of the disease suggest a multi-step process. Recently, a myeloma cell line, NCI-H929, was isolated from a patient with aggressive preterminal disease and found to have a rearranged myc allele. This myeloma cell line has been further characterized in a focus formation assay to determine whether its unusual growth characteristics were associated with a second activated transforming gene. We now report that the NCI-H929 myeloma cell line has an activated rasn allele in addition to a rearranged myc allele. This is the first identification of an activated transforming gene in a multiple myeloma cell line; furthermore, the characterization of two independently activated oncogenes in this B cell malignancy has implications for both the pathogenesis and evolution of the disease.     

Pathophysiological mechanisms of dominant and recessive KVLQT1 K+ channel mutations found in inherited cardiac arrhythmias

The inherited long QT syndrome (LQTS), characterized by a prolonged QT interval in the electrocardiogram and cardiac arrhythmia, is caused by mutations in at least four different genes, three of which have been identified and encode cardiac ion channels. The most common form of LQTS is due to mutations in the potassium channel gene KVLQT1, but their effects on associated currents are still unknown. Different mutations in KVLQT1 cause the dominant Romano-Ward (RW) syndrome and the recessive Jervell and Lange-Nielsen (JLN) syndrome, which, in addition to cardiac abnormalities, includes congenital deafness. Co- expression of KvLQT1 with the IsK protein elicits slowly activating potassium currents resembling the cardiac Iks current. We now show that IsK not only changes the kinetics of KvLQT1 currents, but also its ion selectivity. Several mutations found in RW, including a novel mutation (D222N) in the putative channel pore, abolish channel activity and reduce the activity of wild-type KvLQT1 by a dominant-negative mechanism. By contrast, a JLN mutation truncating the carboxyterminus of the KvLQT1 channel protein abolishes channel function without having a dominant-negative effect. This fully explains the different patterns of inheritance. Further, we identified a novel splice variant of the KVLQT1 gene, but could not achieve functional expression of this nor of a previously described heart-specific isoform.      

Mutations in purine nucleoside phosphorylase deficiency

Purine nucleoside phosphorylase deficiency is an inherited disease of purine metabolism characterized clinically as combined immunodeficiency. The molecular defects have been published for 4 different alleles in 3 patients. We report four new mutations including two amino acid substitutions, A 174P and G190V, a single codon deletion, ΔI129, and a point mutation in intron 3 which leads to aberrant splicing and creation of a premature stop codon in exon 4 (286 -18G→A). Of the previously reported mutations, E89K was found in one additional patient, and R234P was found in 3 unrelated patients, making R234P the most common mutation reported to date in this disease. Hum Mutat 9:118–121, 1997. © 1997 Wiley-Liss, Inc.