Optimizing of the basophil activation test: Comparison of different basophil identification markers.

BACKGROUND: Flowcytometric identification of basophils is a prerequisite for measuring activation of basophils with IgE-dependent or IgE-independent stimuli. Aim of this study was to compare different marker combinations in a simultaneous multicolor flowcytometric measurement. METHODS: Ten patients with a grass pollen allergy and three controls were included in the study. Basophilic cells were gated by using anti-CCR3, anti-IgE, anti-CRTH2, anti-CD203c, and anti-CD3. Cells were activated by a monoclonal anti-FcεRI antibody, N-formyl-methionyl-leucyl-phenylalanine (fMLP), and the allergen extract Phleum pratense. The activation marker anti-CD63 was used. RESULTS: The highest relative number of basophils was found with anti-CCR3+ cells, anti-IgE+ and anti-IgE+ /anti-CD203c+ cells, the lowest with CRTH2+/CD203c+/CD3- cells. A very good and good concordance of CCR3+ cells was seen with CCR3+/CD3- cells and CRTH2+/CD203c+/CD3- cells in all experiments. The contamination of the CCR3+ population with CD3+ cells and the contamination of the IgE+-population with CCR3- cells and CD203- cells were the lowest compared to all other marker combinations. CONCLUSIONS: As the highest relative number of basophils was identified by anti-CCR3 followed by the anti-IgE and anti-IgE/antiCD203c positive population in most cases, these markers can generally be recommended for identification of basophils. If a basophil population with very high purity is needed, anti-IgE should be chosen.

Short-term preseasonal immunotherapy: is early clinical efficacy related to the basophil response?

BACKGROUND: An aluminum hydroxide-adsorbed depot allergoid preparation of six-grass pollen allergens has been developed for short-term preseasonal immunotherapy in pollinosis. However, only limited knowledge exists about its immunological and clinical effects. The aim of this study was to evaluate the basophil response, which can explain early clinical findings of short-term preseasonal allergoid immunotherapy in allergic rhinitis. METHODS: In a double-blind, placebo-controlled study, 31 patients allergic to grass pollens received one course of short-term preseasonal allergoid immunotherapy or placebo. Immunogenicity was assessed by the levels of specific IgG4, IgE antibodies and an allergen-induced CD203c basophil activation test. The primary clinical end point was the combined symptom and medication score/average combined score (ACS). RESULTS: There was a 52.9% difference in ACS between the treatment and placebo groups in favor of immunotherapy (p = 0.01). Active treatment induced Phleum pratense-specific IgG4 and IgE antibodies (p < 0.05). A decrease in allergen-induced basophil activation at submaximal allergen concentrations was demonstrated at the end of immunotherapy and at the peak of the grass pollen season after immunotherapy. CONCLUSIONS: This study shows that grass pollen-allergic patients treated with one course of short-term preseasonal allergoid immunotherapy exhibit a decrease in allergen-induced basophil activation, an increase in allergen-specific IgG4 antibodies and early clinical improvement.

Phl p 3: structural and immunological characterization of a major allergen of timothy grass pollen.

BACKGROUND: The relevant importance of individual allergens for allergic sensitization is only partially understood. More detailed information on allergen structure and how it influences immunological responses can lead to better diagnosis of disease and improved preparations for allergen-specific immunotherapy. Grass pollen contains several different allergens, and although the group 3 allergens have been classified long ago, their structure and allergenicity have been poorly investigated. OBJECTIVE: To characterize Phl p 3 from timothy grass pollen and compare it with Phl p 2 with respect to biochemical structure and allergenicity. METHODS: Natural Phl p 2 and Phl p 3 were separated from a pollen extract by chromatography and characterized by 2D electrophoresis and protein sequencing. The complete sequences were determined by DNA cloning and detected in natural pollen extracts by mass spectrometry. Further comparisons of the allergens were made for IgE-binding and cross-reactivity, allergenicity was determined by basophil CD203c activation and skin prick test and 3D structures were compared by molecular modelling. RESULTS: Phl p 3 reveals molecular masses of 10.958 and 10.973 kDa and pIs of 8.9 and 9.3, respectively, Phl p 2 a molecular mass of 10.816 kDa and a pI of 4.6. The sequence identity is 58%. In spite of these differences in the primary structures, both allergens reveal similar conformational structures, resulting in similar immunological and allergological moieties. CONCLUSIONS: The group 3 and group 2 allergens are major allergens with similar 3D structures. Although they differ considerably in their protein sequences and their pIs, they show only a slightly higher immunological reactivity for Phl p 3 on the B-cell level (conformational epitopes). But distinct differences between the sequences may influence reactivity at the T cell level.

Identification of cytosolic Mg2+-dependent soluble inorganic pyrophosphatases in potato and phylogenetic analysis.

Using polyclonal antibodies raised against a previously cloned potato Mg2+-dependent soluble inorganic pyrophosphatase (ppa1 gene) [8], a second gene, called ppa2, could be isolated. A single locus homologous to ppa2 was mapped on potato chromosomes, unlinked to the two loci identified for ppa1. From a phylogenetic and structural point of view, the PPA1 and PPA2 polypeptides are more closely related to prokaryotic than to eukaryotic Mg2+-dependent soluble inorganic pyrophosphatases (soluble PPases). Subcellular localization by immunogold electron microscopy, using sections from leaf parenchyma cells, showed that PPA and PPA2 are localized to the cytosol. Based on these observations, the likely phylogenetic origin and the physiological significance of the cytosolic soluble pyrophosphatases are discussed.

Analysis of the substrate binding site and carboxyl terminal region of vacuolar H+-pyrophosphatase of mung bean with peptide antibodies.

Vacuolar H+-translocating inorganic pyrophosphatase is a single-protein enzyme and uses a simple substance as an energy donor. Functional domains of the enzyme were investigated by using antibodies specific to peptides corresponding to the putative substrate-binding site (DVGADLVGKVE) in the hydrophilic loop and the carboxyl terminal part. The antibody to the former peptide clearly reacted with the pyrophosphatases of different plant species, and strongly inhibited the hydrolytic activity of the purified enzymes and the proton pumping activity of membrane vesicles. These results indicate that the sequence functions as an actual substrate-binding site and is a common motif. The antibody to the carboxyl terminal part reacted only to the mung bean enzyme, suppressing its hydrolytic and proton pumping activities. The results suggest that the carboxyl terminus is exposed to the cytosol and is close to the catalytic site. H+-Pyrophosphatase hydrolyzed triphosphate and tetraphosphate at low rates. Phytic acid, myo-inositol hexaphosphate, inhibited the enzyme even in the presence of Mg2+. The concentration for 50% inhibition was 0.15 mM. The inhibition of H+-PPase by dicyclohexyldiimide was partly reversed by Mg2+. The catalytic site and the membrane topology of the enzyme are discussed.

Changes in H(+)-pumps and a tonoplast intrinsic protein of vacuolar membranes during the development of pear fruit.

Vacuolar H(+)-ATPase (V-ATPase) was purified from pear fruit and antibodies were raised against the subunits of 55 and 33 kDa. Antibodies against mung bean H(+)-pyrophosphatase (V-PPase) and radish VM23, which is a tonoplast intrinsic protein (TIP) and a water channel, cross-reacted with the vacuolar membrane proteins of pear fruit. To clarify the roles of these proteins in development of pear fruit, we determined their levels relative to the total amount of protein by immunoblot analysis. The levels of subunits of the V-ATPase increased with fruit development. By contrast, the level of V-PPase was particularly high at the cell-division stage and remained almost the same at other stages. The changes in the activities of V-ATPase and V-PPase corresponded to those in their protein levels. The ratio of V-PPase activity to V-ATPase activity indicated that V-PPase is a major H(+)-pump of the vacuolar membranes of young fruit and that the contribution of V-ATPase increases with fruit development, finally, V-ATPase becomes the major H(+)-pump during the later stages of fruit development. The level of a protein analogous to VM23 (VM23P) was especially high during the active cell-expansion stage in young fruit, and VM23P might, therefore, play an important role in the rapid expansion of cells as a vacuolar water channel. Our results show that the levels of V-ATPase, V-PPase and VM23P change differently and reflect the roles of the respective protein in the development of pear fruit.

H(+)-translocating inorganic pyrophosphatase of plant vacuoles. Inhibition by Ca2+, stabilization by Mg2+ and immunological comparison with other inorganic pyrophosphatases.

The effects of divalent cations, especially Ca2+ and Mg2+, on the proton-translocating inorganic pyrophosphatase purified from mung bean vacuoles were investigated to compare the enzyme with other pyrophosphatases. The pyrophosphatase was irreversibly inactivated by incubation in the absence of Mg2+. The removal of Mg2+ from the enzyme increased susceptibility to proteolysis by trypsin. Vacuolar pyrophosphatase required free Mg2+ as an essential cofactor (K0.5 = 42 microM). Binding of Mg2+ stabilizes and activates the enzyme. The formation of MgPPi is also an important role of magnesium ion. Apparent Km of the enzyme for MgPPi was about 130 microM. CaCl2 decreased the enzyme activity to less than 60% at 40 microM, and the inhibition was reversed by EGTA. Pyrophosphatase activity was measured under different conditions of Mg2+ and Ca2+ concentrations at pH 7.2. The rate of inhibition depended on the concentration of CaPPi, and the approximate Ki for CaPPi was 17 microM. A high concentration of free Ca2+ did not inhibit the enzyme at a low concentration of CaPPi. It appears that for Ca2+, at least, the inhibitory form is the Ca2(+)-PPi complex. Cd2+, Co2+ and Cu2+ also inhibited the enzyme. The antibody against the vacuolar pyrophosphatase did not react with rat liver mitochondrial or yeast cytosolic pyrophosphatases. Also, the antibody to the yeast enzyme did not react with the vacuolar enzyme. Thus, the catalytic properties of the vacuolar pyrophosphatase, such as Mg2+ requirement and sensitivity to Ca2+, are common to the other pyrophosphatases, but the vacuolar enzyme differs from them in subunit mass and immunoreactivity.