The recruitment of eosinophils into the airways after allergen exposure is dependent on interleukin (IL) 5 secreted from antigen-specific CD4+ T cells of the T helper cell (Th) 2 subset. However, while it is established that costimulation through CD28 is required for TCR-mediated activation and IL-2 production, the importance of this mechanism for the induction of a Th2 immune response is less clear. In the present study, we administered the fusion protein CTLA-4 immunoglobulin (Ig) into the lungs before allergen provocation to determine whether CD28/CTLA-4 ligands are required for allergen-induced eosinophil accumulation and the production of Th2 cytokines. Administration of CTLA-4 Ig inhibited the recruitment of eosinophils into the lungs by 75% and suppressed IgE in the bronchoalveolar lavage fluid. CTLA-4 Ig also inhibited the production of IL-4, IL-5, and IL-10 by 70–80% and enhanced interferon-γ production from CD3–T cell receptor–activated lung Thy1.2+ cells. Allergen exposure upregulated expression of B7-2, but not B7-1, on B cells from the lung within 24 h. Moreover, airway administration of an anti-B7-2 monoclonal antibody (mAb) inhibited eosinophil infiltration, IgE production, and Th2 cytokine secretion comparable in magnitude to that observed with CTLA-4 Ig. Treatment with an anti-B7-1 mAb had a small, but significant effect on eosinophil accumulation, although was less effective in inhibiting Th2 cytokine production. The anti-B7-2, but not anti-B7-1, mAb also inhibited antigen-induced airway hyperresponsiveness in vivo. In all of the parameters assessed, the combination of both the anti-B7-1 and anti-B7-2 mAb was no more effective than anti-B7-2 mAb treatment alone. We propose that strategies aimed at inhibition of CD28 interactions with B7-2 molecules may represent a novel therapeutic target for the treatment of lung mucosal allergic inflammation.

Interleukin (IL)-4 and IL-5 are two cytokines which synergize in the induction of several biological effector functions. They are produced by mouse and human T helper 2 (Th2) and T helper 0 (Th0) cells. Little is known about the regulation of the two cytokines at the single-cell level. Here we show, using a flow cytometric intracellular staining technique, that IL-4 and IL-5 are predominantly produced by different human peripheral CD4+ and CD8+ T cells, whereas interferon (IFN)-gamma and IL-2 are produced by the same cells. In contrast, cloned human Th0 and Th2 cells were able to produce IL-4 and IL-5 simultaneously. The segregation of IL-4 and IL-5 in activated peripheral T cells was found within 72 h of activation upon anti-CD3 or phorbol ester + ionomycin stimulation. The kinetics of IL-4 and IL-5 production were different at the mRNA and the intra- and extracellular protein level, indicating that the cytokines are regulated differently. T cells from three patients with hyper-IgE syndrome did not display a substantial proportion of IL-4/IL-5 double-positive cells. However, simultaneous production could be induced in normal human T cells after prolonged stimulation with a minimum of two restimulation cycles. We conclude that the simultaneous production of IL-4 and IL-5 is a feature of repetitively activated human T cells.

We studied whether long-lived IgE+ memory B cells develop following three types of primary IgE immune responses. Immunization of mice with anti-IgD antibody induced a T cell-dependent, interleukin (IL)-4-dependent primary IgE response and the formation of IgE isotype switched (IgE+) memory B cells. These IgE+ memory B cells could be stimulated in vivo by injection with goat anti-IgE antibodies to produce a profound IL-4-independent memory IgE response. By contrast, both infection of mice with Nippostrongylus brasiliensis or repeated immunization with benzylpenicilloyl-keyhole limpet hemocyanin (BPO-KLH) in alum stimulated good primary IgE responses and profound memory T cell-dependent antigen-specific IgE responses, but failed to induce the development of long lived IgE+ memory B cells because they could not be recalled with goat anti-IgE antibodies. Mice receiving double immunizations combining anti-IgD with either N. brasiliensis infection or BPO-KLH immunization mounted significant goat anti-IgE-induced secondary IgE responses, but no N. brasiliensis or BPO-KLH-specific IgE could be detected. This indicates that the N. brasiliensis and BPO-KLH induced immune responses do not suppress the development of IgE+ B cells, but rather, do not provide the necessary conditions for their formation. Taken together these data indicate that long-lived IgE+ B cells fail to develop during the primary IgE response to N. brasiliensis infection or BPO-KLH immunization. By contrast, significant numbers of IgE+ memory B cells form during the primary IgE immune response induced by anti-IgD immunization. Our observations suggest that immunization protocols involving membrane IgD cross-linking and limited duration of cognate T cell help are necessary for the formation of IgE+ memory B cells. It will be important to determine the relevance of membrane IgD interaction with allergens, as this would influence the design of new therapies for the treatment of allergy and asthma.

No abstract

Background: Allergies and allergic asthma are believed to be mediated by allergen-specific IgE antibodies. We have investigated the therapeutic potential of inhibiting endogenous IgE by a non-anaphylactogenic anti-mouse IgE antibody 1–5 with respect to its effects on antigen-induced skin reaction, lung function changes and lung inflammation in mice. Methods: Mice were immunized with benzylpenicillinoyl-KLH or ovalbumin, and antigen-mediated skin reaction, bronchoconstriction, bronchopulmonary hyperresponsiveness (BHR) and lung eosinophilic inflammation determined in anti-IgE 1–5-treated versus untreated animals. Results: Application of anti-IgE 1–5 inhibited (by 90%) the serum IgE and, 3–4 days after onset of treatment, blocked the antigen-induced skin reaction. Furthermore, the antibody also inhibited (by 90%) the antigen-induced infiltration of eosinophils into the lung. This latter effect seems to be mediated by blocking the IgE-CD23 interaction and indicates that lung eosinophilic inflammation also depends on IgE. Moreover, when applied to rats passively sensitized with mouse IgE, antibody 1–5 inhibited the antigen-induced bronchoconstriction. A similar effect could be seen in actively immunized mice, where antibody 1–5 was able to inhibit (by 70%) the ovalbumin-induced bronchoconstriction as well as BHR. Conclusions: In summary, non-anaphylactogenic anti-IgE antibodies can markedly inhibit IgE levels and IgE-mediated allergic reactions. Since bronchoconstriction, BHR and lung eosinophilic inflammation can be suppressed, such antibodies may be attractive principles for the treatment of allergic asthma.