Marie Jobin

Allergic rhinitis to ragweed pollen: II. Modulation of histamine-releasing factor production by specific immunotherapy

A number of cytokines, including histamine-releasing factors (HRFs), have a role to play in IgE-mediated asthma. However, the influence of HRF in allergic rhinitis without asthma remains to be revealed. This article presents a double-blind, placebo-controlled study on the role of HRF in ragweed-allergic rhinitis and its modulation by natural pollen exposure and specific immunotherapy (IT). Twenty-seven patients allergic to ragweed were randomly assigned to receive either preseasonal alum-precipitated aqueous extracts of ragweed or placebo. Before the onset of therapy and during the ragweed-pollen season, subjects were evaluated for each of the following: clinical scores, ragweed IgE and IgG antibody levels, and spontaneous and allergen-driven HRF production. Thirteen nonatopic volunteers were also studied in the same protocol. First, before the initiation of therapy, more HRF was produced by both unstimulated and ragweed-stimulated mononuclear cells (MNCs) of atopic subjects as compared to MNCs of nonatopic subjects. Second, MNCs of the placebo-treated group produced significantly more spontaneous and ragweed-specific HRF during the pollen season compared to the preseasonal values. Finally, specific IT not only improved the clinical manifestation of allergy but also prevented the seasonal rise of spontaneous and ragweed-driven HRF production, along with a well-known change in other immunologic parameters associated with successful IT.

Allergic rhinitis to ragweed pollen: I. Reassessment of the effects of immunotherapy on cellular and humoral responses

This work presents a double-blind, placebo-controlled study of 27 patients with allergic rhinitis to ragweed who received preseasonal desensitization immunotherapy [IT] with alum-precipitated aqueous ragweed extracts. We reassessed the following parameters in relation to clinical responses: clinical scores, nasal reactivity to a provocative dose of ragweed causing a 75% fall in airflow rate (PD75), ragweed IgE and IgG, and ragweed-induced basophil histamine release (BHR). First, the nasal PD75 correlated with the severity of nasal symptoms (p less than 0.05). Second, we confirmed a significant symptomatic improvement in the IT-treated group either by clinical scores (p less than 0.05) or the prevention of the seasonal fall of the PD75 (p less than 0.005). Also, IT reduced the seasonal rise of IgE (p less than 0.02) and induced an increase in IgG (p less than 0.01) and a decrease in BHR (p less than 0.03). There was a significant correlation between IgE and BHR (r = 0.80; p less than 0.01). After selecting out the effects of IgE, the BHR was still higher in the placebo-treated group than in the IT-treated group (p less than 0.02), suggesting the involvement of other modulating factors. Symptomatic improvement after IT correlated only with the summation of both IgE and BHR (PD75; r = 0.64; p less than 0.005). This observation suggests that the severity of clinical symptoms is determined by several interacting factors and not by the antibody response alone.

Mapping of Lol p I allergenic epitopes by using murine monoclonal antibodies.

Murine monoclonal antibodies (MAbs) against three non-overlapping epitopes of Lol p I allergen were previously produced and subsequently used for purification of the allergen. In the present study, these MAbs were further characterized, and the biological activity of the purified allergen assessed. The three MAbs were of the IgG isotype and carried a kappa light chain. Their affinity constants were in the range of 7.4-15.1 x 10(-9) mol/l. Purified Lol p I kept its biological activity, as shown by its ability to induce histamine release by basophils of Lol p I-sensitive patients. The profiles of histamine release induced by either Lol p I or crude Lolium perenne extracts were comparable. This observation suggests that human IgE bound to basophils are polyspecific which has been confirmed by immunoblot and inhibition assay. Our data indicated also that Lol p I possesses a major allergenic epitope recognized by all human serum IgE tested. This epitope seems to be partially shared by those recognized by the three MAbs. Finally, preincubation of Lol p I with either one of the Mabs did not affect significantly the basophil-histamine release induced by the purified allergen. This suggests that Lol p I possesses allergenic sites other than the one shared by MAbs and IgE Abs.

Evaluation of Nonspecific Nasal Reactivity to Histamine during and after Natural Ragweed Pollen Exposure

An increased nonspecific nasal reactivity (NSNR) to histamine or to methacholine has been reported in patients with rhinitis, but its contribution to clinical symptoms remains unclear. In the present study, the NSNR to histamine, defined as the concentration of histamine necessary to induce, after a topical challenge, a 75% decrease in nasal airflow (PC75), was significantly more severe in a group of ragweed-allergic subjects during natural exposure to pollen (PC75 = 4.65 mg/ml) than in normal volunteers (PC75 = 12.9 mg/ml, p < 0.0001). However, the basal nasal airflow rates of the two groups were not significantly different (290 and 339 cc). The NSNR correlated with skin sensitivity to ragweed (r = 0.46, p < 0.0021) or with the IgE antibody (Ab) levels (r = 0.42, p < 0.01) but not with the symptom scores. Finally, after the pollen season, the allergic groups nasal sensitivity to histamine improved significantly (PC75 = 4.65 to 9.35 mg/ml, p = 0.03) but remained different from that of the control group (13.19 mg/ml, p = 0.04).

Development of a reverse enzymoallergosorbent test (REAST) to detect timothy-specific IgE antibodies comparison with RAST☆

Radioallergosorbent test (RAST) for the measurement of IgE antibodies has been introduced more than 15 years ago and a number of technical modifications have since improved its sensitivity and reproducibility. The test has been applied to the diagnosis of allergy and to determine changes in the levels of IgE antibodies following immunotherapy. However, specific IgG antibodies are raised during such a therapy and can interfere with the RAST. We have developed a reverse enzymoallergosorbent test (REAST) where microtiter plates are first coated with a purified polyclonal anti-IgE antibody, then with the serum to test and finally with peroxidase-labeled antigen. This assay is antigen specific as shown by the significant inhibition of binding of the labeled antigen in presence of unlabeled specific antigen (greater than 95%) and the absence of inhibition in presence of irrelevant antigens. The values found in atopic patients (85 subjects) were significantly higher than in the non-atopic donors (35 subjects) (1.14 U +/- 1.20 vs. 0.01 U +/- 0.02, P less than 0.0005) and there was a good correlation with the Pharmacia RAST (P less than 0.0005). The levels of specific IgE by both REAST and RAST correlated well with the clinical symptomatology.

Biological activity of monoclonal anti-idiotypic antibody representing the internal image of the major allergenic component of Lolium perenne pollen

Upon immunization with an anti-Lol p I (major allergenic component of Lolium perenne pollen) monoclonal antibody, we have previously produced anti-idiotypic monoclonal antibody (A7H2) displaying some internal image properties. The present study was designated to evaluate the capacity of this anti-idiotypic monoclonal antibody to mimic functionally the antigen by triggering histamine release from basophils of patients allergic to Lol p I. Anti-idiotypic monoclonal antibody, as the antigen, could induce histamine release in a dose-response fashion in all of the atopic patients (6/6). The inhibition of this histamine release by the addition of the idiotype (290A-167) confirmed the specificity of the reaction. Binding inhibition of human IgE to Lol p I demonstrated that the anti-idiotypic antibody recognized an idiotope expressed in the antigen-combining site of IgE molecules. Altogether, these data confirmed the internal properties of our anti-idiotypic antibody and it can mimic the original antigen in its capacity to trigger histamine release.

Effects of H1 and H2 Receptor Agonists on Nonspecific Proliferative Response of Human Peripheral Blood Lymphocytes

Histamine is known to modulate immune responses through the induction of suppressor cell subsets. The inhibition studies with antagonists suggest that the H2 agonist accounts for most of the suppression. This work studies the effects of various concentrations of 3-methyl histamine (as negative control), histamine, and pure H1 (2-methyl histamine, 2-pyridyl ethylamine) and H2 (4-methyl histamine, dimaprit) receptor agonists on the mitogenic (phytohemagglutinin A) proliferative response of normal human lymphocytes. At high concentrations of agonists (10(-3), 10(-4) M) the suppression induced by the two types of agonists is comparable to that of histamine. At lower concentrations (10(-6) M) the suppression is seen only in the presence of the H2 agonist. The suppression induced by the two agonists is generally reversed in the presence of an H2 receptor antagonist. The H1 receptor antagonist did not abolish and even increased the suppression induced by histamine and the two agonists.