Inhibition of murine IgE and immediate cutaneous hypersensitivity responses to ovalbumin by the immunomodulatory agent leflunomide

Abstract

SUMMARYLeflunomide has been identified as an immunoregulatory and anti-inflammatory compound. Allergic disease is characterized by elevated serum IgE levels, production of allergen-specific IgE and the release of inflammatory mediators from mast cells and granulocytes. Here we demonstrate, using an in vivo murine model, the ability of leflunomide to down-regulate levels of total and allergen-specific serum IgE production. Mice receiving leflunomide (45 mg/kg) orally at the time of primary immunization with ovalbumin adsorbed to aluminium hydroxide adjuvant, showed a reduction in total serum IgE levels of 95%, 41% and 32% following primary, secondary and tertiary immunizations, respectively (P < 0·05). When leflunomide was administered both at the time of primary and subsequent immunizations, reductions in total and specific serum IgE levels of > 80% and > 38%, respectively, were observed (P < 0·05). Administration of leflunomide to mice which had already developed an IgE response resulted in reductions in total and specific serum IgE levels of > 80% and > 45%, respectively (P < 0·05). Following leflunomide treatment, animals failed to develop immediate cutaneous hypersensitivity responses when challenged intradermally with allergen. Down-regulation of immunoglobulin production was not restricted to IgE, since levels of allergen-specific IgG1 and IgG2a in serum were also reduced. The finding of significant reductions in total and allergen-specific IgM suggests that the mechanism of action does not involve selective inhibition of immunoglobulin class switching. A loss in production of the T helper cell-derived B cell differentiation factor IL-5 may account for the reduction in immunoglobulin levels. In adoptive transfer experiments leflunomide did not induce tolerance in allergen-reactive Th2 populations, contrary to animal disease models of transplantation and autoimmunity, where leflunomide was shown to induce tolerance in the effector T cell population.

Interleukin-10-Treated Dendritic Cells Do Not Inhibit Th2 Immune Responses in Ovalbumin/Alum-Sensitized Mice

“…Recently, we have demonstrated that IL-10-treated DC are able to inhibit allergen-specific Th1 and Th2 cytokine production by T cells from atopic individuals in vitro [8]. In the present study, we used the well-established mouse models of type I allergy and of allergic inflammation [24] to analyze the effect of transfer of IL-10-treated DC in vivo on the development of Th2 responses induced by intraperitoneal injections of low doses of OVA/alum. We have demonstrated that in contrast to transfer of OVA-pulsed, but IL-10-untreated, DC prior to sensitization, which led to enhanced proliferation and cytokine production by mesenterial lymph node cells after restimulation with OVA in vitro, transfer of OVA-pulsed IL-10-treated DC did not increase CD4+ T-cell proliferation nor Th1 and Th2 cytokine production.…”

Efficacy of recombinant adenovirus as vector for allergen gene therapy in a mouse model of type I allergy

“…ELISA for determination of ␤gal-specific antibodies in serum ␤Gal-specific antibodies of different isotypes (IgG1, IgG2a, IgE) were measured using an antigen capture ELISA as reported 56 with modifications. All reagents except the blocking buffer were used in volumes of 100 l/well.…”

Formalin-Fixed <i>Staphylococcus aureus</i> Particles Prevent Allergic Sensitization in a Murine Model of Type I Allergy

“…It has been shown previously that protein A, a cell wall component of most S. aureus strains, exhibits immunomodulatory properties, including the induction of Th1 responses after intraperitoneal administration [35]. Therefore, it was tempting to speculate that the expression of protein A might contribute to the Th1-biasing capacity of S. aureus particles.…”

“…Allergen sensitization of mice was induced by repeated intraperitoneal injection of 10 µg ovalbumin (OVA Grade VI; Sigma-Aldrich, Deisenhofen, Germany) adsorbed to aluminum hydroxide (alum; Pierce, Rockford, Ill., USA) at intervals of 2 weeks [35]. In order to determine the effect of application of S. aureus on the OVA-specific immune response, mice were injected with a total volume of 200 µl containing OVA/alum and 10 9 formalin-fixed S. aureus particles, Cowan I strain (SACS; Pansorbin; Calbiochem-Merck Biosciences, Bad Soden, Germany) or protein A-free Wood 46 strain (SAWS; Sigma-Aldrich) as indicated.…”

“…Sera were collected and frozen at –20°C until thawed for analysis. Determination of OVA-specific Ab by ELISA was performed as reported [35] with the modification that o-phenylenediamine was used as substrate [36]. The optical density (OD) was measured in a microplate reader E max (MWG-Biotech, Ebersberg, Germany) at 490 nm.…”