Arturo Genovese

Pure Red Cell Aplasia: Studies on an IgG Serum Inhibitor Neutralizing Erythropoietin

Summary. A new type of IgG serum inhibitor in adult pure red cell aplasia (PRCA) has been investigated. This inhibitor is directed against circulating erythropoietin (Ep) (PRCA type B), rather than the erythroid marrow (PRCA type A). Thus, the IgG inhibitor, after interaction with Ep in solution, is precipitated together with Ep by addition of goat anti‐human gamma‐globulins. Pre‐therapy PRCA serum, although apparently devoid of Ep, shows considerable Ep activity following acidification and boiling. The inhibitor is absent from post‐therapy serum, while Ep levels are elevated. An experimental model for PRCA type B has been established in normal mice after prolonged administration of pre‐remission serum IgG.

Immunological characterization and functional importance of human heart mast cells

Mast cells are present in normal and even more abundant in diseased human heart tissue and their localization is of particular relevance to their function. Within heart tissue mast cells lie between myocytes and in close contact with blood vessels. They are also found in the coronary adventitia and in the shoulder regions of a coronary atheroma. The density of cardiac mast cells is markedly higher in some patients with myocarditis and dilated cardiomyopathy than in accident victims without cardiovascular diseases. More importantly, in some of these conditions there is in situ evidence of mast cell activation. We have described an original technique to isolate and purify HHMC for in vitro study. This procedure gives viable cells and after stimulation with immunological or non-immunological stimuli they release performed (histamine and tryptase) and newly generated mediators (PGD2 and LTC4). We have demonstrated that HHMC differ from those in other anatomical districts in that they are activated by specific immunological and non-immunological stimuli, and in their relation to the arachidonic acid metabolism, suggesting that the local microenvironment can influence their phenotypic and biochemical characteristics. Our own and other findings suggest that HHMC have complex and significant roles in different pathophysiological conditions involving the cardiovascular system. Direct activation of HHMC by therapeutic and diagnostic substances injected intravenously explains some of the anaphylactoid reactions caused by these agents. HHMC possess Fc epsilon RI and IgE bound to the surface and C5a receptors, which could explain how cardiac mast cells are involved in systemic and cardiac anaphylaxis. Cardiac mast cells and those in human coronary arteries also play a role in the early and late stages of atherogenesis and during ischemic myocardial injury. In conclusion, although studies of HHMC are in their infancy, their in vitro isolation may be useful in identifying additional mediators synthesized and released, stimuli relevant to human pathophysiology, and pharmacological agents selectively modulating the activation of these cells and their mediators. Drugs specifically acting on HHMC or on their mediators may eventually be useful in treating different cardiovascular diseases.

Loratadine and desethoxylcarbonyl-loratadine inhibit the immunological release of mediators from human FceRI+cells

Background Loratadine, a novel histamine H1‐receptor antagonist, is effective in the treatment of patients with seasonal and perennial rhinitis and some allergic skin disorders. Histamine and other chemical mediators are synthesized and immunologically released by human peripheral blood basophils and tissue mast cells (FcɛRI+ cells).

Angiogenesis and lymphangiogenesis in bronchial asthma

To cite this article: Detoraki A, Granata F, Staibano S, Rossi FW, Marone G, Genovese A. Angiogenesis and lymphangiogenesis in bronchial asthma. Allergy 2010; 65: 946–958.

Expression and functions of the vascular endothelial growth factors and their receptors in human basophils.

Angiogenesis is a multistep complex phenomenon critical for several inflammatory and neoplastic disorders. Basophils, normally confined to peripheral blood, can infiltrate the sites of chronic inflammation. In an attempt to obtain insights into the mechanism(s) underlying human basophil chemotaxis and its role in inflammation, we have characterized the expression and function of vascular endothelial growth factors (VEGFs) and their receptors in these cells. Basophils express mRNA for three isoforms of VEGF-A (121, 165, and 189) and two isoforms of VEGF-B (167 and 186). Peripheral blood and basophils in nasal polyps contain VEGF-A localized in secretory granules. The concentration of VEGF-A in basophils was 144.4 ± 10.8 pg/106 cells. Immunologic activation of basophils induced the release of VEGF-A. VEGF-A (10–500 ng/ml) induced basophil chemotaxis. Supernatants of activated basophils induced an angiogenic response in the chick embryo chorioallantoic membrane that was inhibited by an anti-VEGF-A Ab. The tyrosine kinase VEGFR-2 (VEGFR-2/KDR) mRNA was expressed in basophils. These cells also expressed mRNA for the soluble form of VEGFR-1 and neuropilin (NRP)1 and NRP2. Flow cytometric analysis indicated that basophils express epitopes recognized by mAbs against the extracellular domains of VEGFR-2, NRP1, and NRP2. Our data suggest that basophils could play a role in angiogenesis and inflammation through the expression of several forms of VEGF and their receptors.

Bacterial Immunoglobulin Superantigen Proteins A and L Activate Human Heart Mast Cells by Interacting with Immunoglobulin E

ABSTRACT Human heart mast cells (HHMC) have been identified in heart tissue, perivascularly, and in the intima of coronary arteries. In vitro activation of isolated HHMC induces the release of vasoactive and proinflammatory mediators (histamine, tryptase, and cysteinyl leukotriene C4 [LTC4]). We investigated the effects of several bacterial proteins on HHMC activation in vitro. HHMC released histamine, tryptase, and LTC4 in response toStaphylococcus aureus Cowan 1 and the immunoglobulin (Ig)-binding protein A, but not to S. aureus Wood 46, which does not synthesize protein A. The effect of protein A was inhibited by preincubation with monoclonal IgM VH3+. Some strains of Peptostreptococcus magnus express an Ig light chain-binding surface protein called protein L. Such bacteria and soluble protein L stimulated the release of preformed and newly synthesized mediators from HHMC. Preincubation of HHMC with either protein A or protein L resulted in complete cross-desensitization to a subsequent challenge with the heterologous stimulus or anti-IgE. Monoclonal IgE (κ chains) blocked protein L-induced release, whereas IgE (λ chains) had no effect. Streptococcal protein G, formyl-containing tripeptide, and pepstatin A did not activate HHMC. Bacterial products protein A and protein L and intact bacteria (S. aureus and P. magnus) activate HHMC by acting as Ig superantigens.

Cardiac ion channels and antihistamines: possible mechanisms of cardiotoxicity

Despite the enormous success of second generation antihistamines, in the mid‐1980s, about 10 years after their introduction in the market, several reports appeared in the literature indicating the rare occurrence of a form of polymorphic ventricular dysrhythmia, the ‘torsade de pointes’, after the administration of astemizole or terfenadine. This cardiac side‐effect has been interpreted as a consequence of the interference of these drugs with cardiac K+ channels involved in action potential repolarization, and in particular with the IKr component of the cardiac repolarizing current. As the K+ channels encoded by the human ether‐a‐gogo‐related gene (HERG) seem to represent the molecular basis of IKr, this cardiac K+ channel was soon recognized as a primary target for second generation antihistamine‐induced proarrhythmic effects. In fact, both terfenadine and astemizole have been shown to block HERG K+ channels in a concentration range similar to that found in the plasma of subjects with cardiotoxic manifestations. However, no correlation can be found between the ability to prolong the cardiac action potential duration and the H1‐antagonistic activity by several antihistamines, suggesting that HERG blockade and cardiotoxic potential are not class properties of second generation antihistamines. In fact, other molecules such as cetirizine, loratadine, acrivastine, and fexofenadine seem to lack both cardiotoxic potential and HERG‐blocking ability at therapeutically relevant concentrations. The marked heterogeneity displayed by second generation antihistamines in their ability to prolong the cardiac action potential duration and to block HERG K+ channels might be of considerable therapeutical significance for those patients at risk of developing cardiac dysrhythmias and in need of therapy with H1‐receptor blockers; it also emphasizes the importance of an evaluation of the possible blockade of HERG K+ channels during the early developmental phases of novel compounds belonging to this therapeutical class.

Role of Mast Cells, Basophils and Their Mediators in Adverse Reactions to General Anesthetics and Radiocontrast Media

General anesthetics and radiocontrast media (RCM) can cause anaphylactic or anaphylactoid reactions. These are usually underdiagnosed and underreported, but their incidence is apparently rising. Their pathogenesis is complex and not completely understood, but the release of vasoactive mediators from basophils and mast cells plays a central role. The recent development of in vitro techniques to study the release of preformed (histamine and tryptase) and de novo synthesized mediators (PGD2, LTC4, and PAF) from purified basophils and mast cells has made it possible to quantify the mediator-releasing activity of anesthetics such as muscle relaxants, general anesthetics, opioids, and benzodiazepines and RCM on human basophils and mast cells isolated from lung, skin and heart tissues. The majority of general anesthetics and RCM tested induced only the release of preformed mediators (histamine and tryptase), not of the de novo synthesized eicosanoids. There was wide variability in the response of basophils and mast cells from different donors to the same drug or RCM, presumably due to the releasability parameter. Hyperosmolality is probably not the only factor responsible for basophil and mast cell activation by RCM. The in vitro release of histamine induced by anesthetic drugs and RCM was correlated with the release of tryptase. Given the longer half-life of tryptase than histamine in plasma, measurements of plasma tryptase may become a useful diagnostic tool for identifying adverse reactions to anesthetics and RCM.

Immunoglobulin Superantigen Protein L Induces IL-4 and IL-13 Secretion from Human Fc varepsilon RI(+) Cells Through Interaction with the kappa Light Chains of IgE.

Peptostreptococcus magnus protein L is a multidomain bacterial surface protein that correlates with virulence. It consists of up to five homologous Ig-binding domains (B1–B5) that interact with the variable domain of Ig κ L chains. Intact protein L stimulates the synthesis and the release of IL-4 and IL-13 from human basophils in vitro. A protein L fragment covering the Ig-binding domains B1–B4 also induced IL-4 and IL-13 release from basophils. There was an excellent correlation (rs = 0.82; p < 0.001) between the maximal percent IL-4 release induced by protein L and that induced by anti-IgE and between intact protein L and the B1–B4 fragment (rs = 0.90; p < 0.01). Removal of IgE bound to basophils markedly reduced the IL-4 release induced by anti-IgE, protein L, and B1–B4. Preincubation of basophils with protein L or anti-IgE caused complete cross-desensitization to subsequent challenge with the heterologous stimulus. IgE purified from myeloma patients PS and PP (λ chains) blocked anti-IgE-induced IL-4 release, but not the releasing activity of protein L. In contrast, IgE purified from myeloma patient ADZ (κ chains) blocked both anti-IgE- and protein L-induced secretion. Cyclosporin A, but not cyclosporin H, inhibited protein L-induced release of IL-4 and IL-13 from basophils. Thus, protein L acts as a bacterial Ig superantigen to induce the synthesis and release of IL-4 and IL-13 from basophils by interacting with κ L chains of the IgE isotype.

Role of human mast cells and basophils in bronchial asthma.

Mast cells and basophils are the only cells expressing the tetrameric (alphabetagamma2) structure of the high affinity receptor for IgE (FcepsilonRI) and synthesizing histamine in humans. Human FcepsilonRI+ cells are conventionally considered primary effector cells of bronchial asthma. There is now compelling evidence that these cells differ immunologically, biochemically, and pharmacologically, which suggests that they might play distinct roles in the appearance and fluctuation of the asthma phenotype. Recent data have revealed the complexity of the involvement of human mast cells and basophils in asthma and have shed light on the control of recruitment and activation of these cells in different lung compartments. Preliminary evidence suggests that these cells might not always be detrimental in asthma but, under some circumstances, they might exert a protective effect by modulating certain aspects of innate and acquired immunity and allergic inflammation.