Identification of anti-idiotypic antibodies in the sera of ryegrass-allergic and nonallergic individuals

Anti-ids in allergy: timeliness of a classic concept

Abstract:

Anti-idiotypic antibodies (anti-ids) are part of natural immune responses with regulatory capacity. Their effect on an antigen-specific, so-called Ab1 antibody response, is dependent on 1) the original antigen, which they mirror, being Ab2 antibodies, and 2) their isotype. In the case of IgE-mediated allergy, natural anti-ids against allergen-specific IgE represent internal images of allergen molecules. A key biologic feature of allergens is that they can crosslink IgE, expressed by B-lymphocytes or passively bound via high affinity receptors to effector cells, which renders cellular activation. Therefore, the IgE cross linking capability of anti-ids determines whether they dampen or enhance immediate-type hypersensitivity. Correspondingly to classic antiallergen blocking IgG antibodies, anti-ids may also interact with inhibitory FcγRIIb receptors and, thereby, down-regulate T_H2-type inflammation. Anti-ids and other B-cell epitope mimetics, like mimotopes and DARPins, represent antigen surrogates, which can be used for vaccination. Intriguingly, they may induce antibody responses without activating potentially proinflammatory, antiallergen T-lymphocytes. Taken together, collective evidence suggests that anti-ids, although representing immunologic classics, are a timeless concept in allergology.

Circulating cat allergen and immune complexes in cat-allergic children

BACKGROUND

The first encounters with allergens seem to influence the development of allergy. Food antigens have been detected in sera as free antigens and in complexes with IgG but less is known about the presence of inhalant allergens.

OBJECTIVE

To investigate the presence of the major cat allergen Fel d 1, either as free allergen and/or in complexes with IgG and IgE antibodies in sera from atopic children.

METHODS

Serum samples from 33 cat allergic asthmatic children, 7-17 years old, and 15 non-allergic controls were investigated for the presence of Fel d 1 by ELISA (detection limit 0. 13 microg/L). To detect immune complexes (IC), the IgG fraction from Fel d 1 positive sera was purified by affinity chromatography. Purified and non-absorbed material was then analysed for allergen content and specific IgG antibody levels. Immune complexes with Fel d 1 IgE were detected by coupling anti-Fel d 1 MoAb to paramagnetic particles.

RESULTS

Fel d 1 was detected (0.15-1.8 microg/L) in 23 of the 33 patients (70%) but not from any of the controls. Eighteen samples contained IgE-Fel d 1 IC and two of four tested samples contained Fel d 1 in the IgG fraction. Electrophoresis and Western blotting of IgG purified material using anti-Fel d 1 MoAb corroborated the presence of IgG-Fel d 1 IC.

CONCLUSION

Free-circulating inhalant allergen and IC with allergens may contribute to maintaining immune responsiveness and sensitivity.

Anti-IgE and anti-Fc epsilon RI autoantibodies in clinical allergy

Autoantibodies recognizing critical effector molecules of type I allergic reactions have been identified. Anti-IgE autoantibodies occur at high frequencies not only in atopic diseases but also in healthy individuals and, depending on their epitope specificities, may promote or prevent the elicitation of allergic symptoms. In contrast, anti-Fc epsilon RI autoantibodies with basophil/mast cell activating properties were selectively found in patients with chronic urticaria, a condition characterized by the continuous degranulation of mast cells. Thus, humoral anti-Fc epsilon RI autoreactivity defines a distinctive subset of chronic urticaria and may well be the causative and pathogenetic principle in this disease.

Human auto-anti-idiotypic antibodies to mite-specific IgE can degranulate human basophils in vitro

BACKGROUND

Anti-idiotypic antibodies (anti-Ids) to specific IgE antibodies are formed spontaneously during an anti-allergen immune response and can be induced by immunotherapy. Although anti-Ids can down-regulate the production of IgE antibodies, at least in experimental models, their possible role in the modulation of target cell reactivity remains ill-defined.

OBJECTIVE

The capacity of human anti-Ids to modulate the release of histamine was examined in an in vitro system of human basophil degranulation. Anti-Ids were prepared from the serum of six Dermatophagoides pteronyssinus (Dp)-hypersensitive patients suffering from atopic dermatitis and who had never been desensitized. Basophils were obtained from the blood of atopic donors. The extent of histamine release was determined using a fluorometric assay.

RESULTS

We show that: anti-Ids trigger the release of histamine in an allergen-specific, dose- and IgE-dependent manner; the release is not due to the presence of allergen and/or anti-IgE antibodies; and that the degranulating activity can be removed by absorption with affinity-purified anti-Dp antibodies of the corresponding patient.

CONCLUSION

These results indicate that spontaneously produced human anti-Ids can modulate the reactivity of human basophils.

Possible dual role of anti-idiotypic antibodies in combined passive and active immunotherapy in honeybee sting allergy

BACKGROUND

Passive infusion of beekeepers' plasma was shown to protect patients against systemic reactions occurring during active immunotherapy by mechanisms still to be clarified. It is tempting to speculate that anti-idiotypic antibodies could play a role because they are found in beekeepers' plasma and are involved in the regulation of IgE synthesis.

METHODS

In this report we studied the effects of passive infusion of a beekeeper's plasma rich in anti-idiotypic antibodies to a patient who experienced systemic reactions to honeybee venom.

RESULTS

We reported, during the days after the infusion, a decrease of clinical sensitivity to the honeybee venom. Indeed, the patient tolerated a cumulative dose of 280 micrograms of venom without adverse reactions. We also observed decreases in skin mast cell and in basophil sensitivity. After the plasma infusion, a modified rush immunotherapy with honeybee venom was initiated in our patient. In the following 76 weeks, increased levels of anti-idiotypic antibodies in the serum of the patient were associated with a diminution of specific antibodies (IgG and IgE) to honeybee venom.

CONCLUSION

These results suggest a dual role of anti-id in our combined protocol of passive and active immunotherapy: an immediate action on clinical sensitivity along with a decrease of skin mast cell and basophil sensitivity and an immunoregulatory role on specific antibody production.

Human anti-IgE antibodies by repertoire cloning

Anti-IgE antibodies have been detected in sera of patients with an allergic disease where they might play a role in the regulation of (Ig)E-mediated reactions. Using a recombinant phage surface display expression system a combinatorial library of antibody heavy and light chains was constructed from peripheral blood mononuclear cells from an atopic donor immunized with tetanus toxoid. Screening of the library allowed the identification of a large number of phages displaying human monovalent antigen-binding fragments (Phab) against tetanus toxoid and IgE. Surprisingly, we found a high frequency of Phab against particular IgE myelomas that was comparable to the frequency found for Phab against tetanus toxoid. However, most of these Phab were directed to different idiotypic determinants, depending on the IgE myeloma used for the panning procedure. Nevertheless, two clones were found to have anti-isotypic specificity and were shown to react specifically with the CH2 domain of the IgE heavy chain.