Detection of allergens in a cat pelt extract

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.

Role of animal danders as inhalant allergens in bronchial asthma in India

The etiological significance of animal danders in Indian patients with nasobronchial disorders has not yet been investigated. In the present study, the role of animal danders in the etiology of bronchial asthma was studied. Extracts of danders from 6 animals along with guinea pig whole pelt were prepared. Intradermal and bronchial provocation tests with these extracts were performed on (i) 68 asthmatics and (ii) 20 nonallergic healthy volunteers. In patients, significant positive skin reactions (2+ to 4+) ranged from 1.4% each with guinea pig whole pelt and ox dander to 8.8% with dog dander extracts. None of the healthy volunteers elicited such a response. On bronchial provocation, 20% and 53.8% of the tests were positive in asthmatics showing 1+ and 2+ skin reactivity, respectively. All the patients as well as controls eliciting negative intradermal responses demonstrated uniformly negative bronchial provocation tests to different dander extracts. Analysis of various clinical features of asthmatics with respect to skin positivity to dander/pelt extract was also carried out. Radioallergosorbent tests (RASTs) were performed to estimate dander-specific IgE levels in the sera of patients showing different grades of skin response to dander extracts of dog, horse, and goat. Sixty percent of sera from the patients showing 2+ to 4+ skin reactivity to various animal dander extracts showed positive RASTs. RAST positivity as well as RAST ratio increased with increase in the intensity of skin response. All the patients with positive cutaneous as well as positive bronchial responses also showed positive RASTs. Similarly, all the patients with positive skin and positive RASTs showed positive bronchoprovocation tests. These results suggested that animal danders play an important role in the etiology of bronchial asthma. Some of the clinical characteristics of asthmatics, such as (i) early age at onset of asthma, (ii) positive family history, and (iii) asthma with associated allergies, have significant bearing on the cutaneous response to various dander extracts.

Environmental control of allergens

Allergy therapy properly consists of three possible treatment methods that can be used singly or in combination: environmental control (avoidance), pharmacotherapy, and immunotherapy. What allergens are effectively treated by environmental control? There are several broad groups of allergens with which we are concerned: indoor allergens such as dust, animal dander, molds (indoor), and cockroach; and outdoor allergens such as trees, grasses, weeds, and molds (outdoor); and, lastly, foods. The largest body of work has been collected regarding the effectiveness of indoor allergens, especially dust mites and cat. Scientifically proven measures exist for dust mites, cats, and infant formulas. Practical advice for controlling the environment for other furred animals, cockroaches, molds, and pollens are summarized. More research on effective avoidance measures for these other allergens is needed to help our patients control their environment effectively.