Ennio Leggieri

Study of the effects of paf‐acether on human nasal airways

In 6 normal subjects and 6 patients with allergic rhinitis, nasal response to insufflation of paf‐acether (paf, platelet‐activating factor), lyso‐paf and histamine was evaluated. Nasal challenge with paf, at doses of 300 and 600 nM, induced nasal obstruction, associated with an increase in nasal airway resistances, measured by antherior passive rhinomanometry. Maximum increase in nasal airway resistance was observed at 30 min after challenge (mean percent change + 481 with 600 nM paf; P < 0.05). Other symptoms induced by paf insufflation were rhinorrhea (6 out of 12 subjects), itching (8 out of 12), sneezing (4 out of 12) and a burning sensation (6 out of 12). No differences were observed between normal and rhinitic subjects, concerning nasal sensitivity to paf. Neither nasal symptoms nor changes in nasal airway resistance were observed after nasal challenge with lyso‐paf (300 and 600 nM); by contrast, histamine (100 nM) induced sneezing, nasal obstruction, itching and rhinorrhea in all the studied subjects, associated with an increase in nasal airway resistance (maximum 5 min after challenge: percent change + 358; P < 0.02). Nasal effects of paf were not mediated by histamine, since no increase in histamine levels was observed in nasal washings following paf insufflation. We conclude that paf may have pathogenetic relevance in allergic rhinitis.

Mediators and Allergic Inflammation of Human Airways

Local antigen challenge in patients with respiratory allergy is associated with histamine and arachidonic acid metabolites release, both in upper and in lower respiratory airways. Raised histamine levels can be detected in nasal secretions 5 min after allergen stimulation. Increased leukotriene C4 and prostaglandin D2 concentrations persist for a longer period (respectively 20 and 30 min). Endobronchial antigen stimulation is also followed by release of histamine, leukotriene C4 and prostaglandin D2, which can be detected in bronchial lavage fluid. Elevated concentrations of these mediators can be found 5 and 15 min after challenge. Moreover, endobronchial antigen stimulation is associated with an increase in the number of bronchial epithelial cells recovered in bronchial lavage fluids.

Study of the effect of some neuropeptides and endogenous opioid peptides on in vitro histamine release from human lung mast cells and peripheral blood basophils

In the present study we investigated the effect of substance P, bombesin, beta lipotropin, alpha and gamma endorphins, and metionin and leucin enkephalins onin vitro histamine release from partially purified human lung mast cells and peripheral blood basophils.In the concentration range of 10–100 μM, these neuropeptides and endogenous opioid peptides neither elicited a significant histamine secretions from human lung mast cells and blood basophils, nor influenced the anti-IgE-induced histamine release. These data indicate that human lung mast cells and blood basophils are resistant to the activity of substance P, bombesin, beta lipotropin, alpha and gamma endorphins, and metionin and leucin enkephalins, and confirm the functional heterogeneity of mast cells, depending on the species and the tissue origin.

Enhanced basophil releasability in subjects infected with human immunodeficiency virus

Spontaneous histamine release and basophil response to IgE-dependent (anti-IgE) and IgE-independent (formyl-methionine peptide, calcium ionophore A23187) stimuli were evaluated in 15 patients with acquired immunodeficiency syndrome (AIDS), 8 with AIDS related complex (ARC), 7 with lymphadenopathy syndrome (LAS), 11 seropositive asymptomatic subjects, 10 human immunodeficiency virus (HIV)-seronegative drug addicts, and 20 normal subjects. Both spontaneous histamine release and anti-IgE-induced histamine release were significantly increased in HIV-infected subjects, in comparison with seronegative drug addicts and normal controls. Basophil response to anti-IgE was higher in AIDS/ARC patients than in seropositive asymptomatic subjects and LAS patients, although the difference was not statistically significant. When basophils were challenged with 0.1 microM formyl-methionine peptide, a significantly increased histamine secretion was found in HIV-infected subjects; conversely, at the higher formyl-methionine peptide concentration (10 microM), as well as at all calcium ionophore A23187 concentrations, histamine release was similar in all the studied groups. No correlation was found among anti-IgE-induced histamine release, total lymphocyte counts, CD4+ and CD8+ T cell counts, and total serum IgE levels. These findings indicate that infection with HIV is associated with an increased basophil releasability. This could be of some relevance in the increased incidence of allergic manifestations and adverse drug reactions observed in AIDS patients.

Cord Blood Basophil Releasability: Evaluation of Histamine Release and Leukotriene C4 Generation

This study was performed to evaluate mediator (histamine and leukotriene C4) release from cord blood and adult blood basophils, challenged with IgE-independent (calcium ionophore A23187) and IgE-mediated (anti-IgE) stimuli. IgE-independent mediator release was similar in adult blood and umbilical blood basophils. Conversely, the anti-IgE-induced histamine and immunoreactive leukotriene C4 (iLTC4) release was significantly reduced in cord blood basophils. Passive sensitization with an IgE-rich serum was followed by a significant increase in the number of eluted IgE molecules from cord blood basophils and by an increase in IgE-mediated histamine release. iLTC4 production was not affected by passive sensitization of umbilical blood basophils. The IgE-dependent mediator release from cord blood basophils was not correlated with the number of cell-bound IgE. In addition, histamine secretion and leukotriene C4 production from cord blood basophils seem to be independent events.

Functional Evaluation of the Basophil/IgE System in the Cord Blood

Basophil releasability was studied in 24 cord blood samples from normal-term deliveries. The histamine content in cord blood basophils was similar to that of adult blood basophils. The response to IgE-independent degranulating stimuli such as calcium ionophore A23187 and zymosan-activated human serum was overlapping with that of normal adults. Conversely, a reduced releasability was observed after challenge with anti-IgE, even after sensitization with an IgE-rich serum. The IgE-dependent degranulation seems to be hampered by the low concentrations of circulating and cell-bound IgE antibodies. The number of IgE molecules bound to the specific receptors in cord blood basophils is significantly lower than in adult blood basophils.

Basophil activation in idiopathic mixed cryoglobulinemia

We studied basophil activation in patients affected by idiopathic mixed cryoglobulinemia in order to investigate the role of the basophil cell in the pathogenesis of the vasculitis typical of this disease. We selected 13 patients and we performed thein vitro basophil degranulation test with cryoprecipitate; in 5 cases the test was positive when it was performed in whole blood, while it was negative when it was performed with cells washed and resuspended in Tyrodes buffer. In 6 subjects it was not possible to perform the test because of the very low number of circulating basophil cells. Finally, in 2 subjects thein vitro basophil degranulation test with cryoprecipitate was negative; this result may be related to the very low levels of complement factors in the sera of these subjects. These findings sugges that the pathogenetic mechanism of vasculitis in idiopathic mixed cryoglobulinemia could be started by basophil activation.

Effect of nitrendipine on histamine release from human basophil leukocytes

The effect of the new calcium antagonist nitrendipine on in vitro basophil activation was evaluated in 10 subjects. The histamine release induced by calcium ionophore A23187, f‐met peptide and anti‐IgE was inhibited, in a dose‐dependent fashion, by nitrendipine in the concentration range of 1–100 μM. The activity of this calcium antagonist seems complex and related to an interference with calcium at multiple sites. At concentrations higher than 200 μM, nitrendipine causes histamine release from basophil leukocytes. This histamine secretion is likely to be due to a cytotoxic effect, since it is associated with an increase in LDH levels in the cell supernatant.

Clonidine inhibits IgE-mediated and IgE-independent in vitro histamine release from human basophil leukocytes.

Clonidine, a common antihypertensive agent, was recently shown to inhibit antigen-induced wheal and flare reactions, as well as allergen-evoked bronchoconstriction in allergic patients. In this study we investigated the in vitro anti-allergic properties of clonidine. This alpha 2 adrenoceptor agonist inhibited, in a dose-dependent fashion, basophil histamine secretion elicited by anti-IgE and f-met peptide; it also blocked, though to a lesser extent, the calcium ionophore A23187-induced histamine release. H2 receptor stimulation seems to be responsible for the reduction in histamine release observed, since it can be antagonized by cimetidine, but not by alpha 1, alpha 2 and H1 blockers.

Functional characterization of specific IgE antibodies for tetanus toxoid

SummaryThe specific IgE response that appears in subjects immunized with tetanus toxoid does not induce hypersensitivity reactions at subsequent immunizations. The type I immune response, therefore, was studied bothin vivo andin vitro, in 11 subjects who had specific IgE antibodies for tetanus toxoid. The results showed that: 1. the specific IgE antibodies are heterogeneous regarding their affinity for the mast cell and basophil receptors; 2. the specific IgG antibodies for tetanus toxoid, at serum concentrations, are not able to interfere with thein vitro specific basophil degranulation; 3. in the PEG precipitare there are aggregates of specific IgE antibodies for tetanus toxoid.In vitro, these molecular aggregates are not able to sensitize the basophil cells.