Total and allergen-specific immunoglobulin A levels in saliva in relation to the development of allergy in infants up to 2 years of age.

BACKGROUND: The association between salivary IgA levels and development of allergy is controversial and the employed methodology has been questioned. OBJECTIVE: The aim of the study was to relate the levels of total IgA, SIgA and allergen-specific IgA antibodies in saliva to the development of allergy in infants during the first 2 years of life. METHODS: Saliva samples from 80 infants participating in a prospective study regarding the development of allergy were collected at 3 or 6, and 12 and 24 months of age. Total IgA, SIgA and Fel d 1 and beta-lactoglobulin specific IgA levels were analysed with ELISA. RESULTS: The levels of total IgA and SIgA increased with age. The number of samples with detectable IgA to Fel d 1 tended to increase with age, whereas the opposite was observed for IgA to beta-lactoglobulin. Infants who developed allergy tended to have higher levels of total IgA, and allergen-specific IgA was more commonly detected than in non-allergic children. In contrast, non-allergic children tended to have higher levels of SIgA. Furthermore, the levels of SIgA were higher in sensitized infants with no allergic symptoms than in sensitized children with symptoms. Infants with allergic parents had lower SIgA levels than infants without. Direct exposure to cat and cow's milk did not influence the levels of allergen-specific IgA levels, nor was there any association between breast-feeding and IgA production. CONCLUSION: The kinetics of food and inhalant allergen-specific IgA in saliva during the first 2 years of life is similar to what has earlier been shown for IgG in serum. Development of allergy tended to be associated with high levels of total and allergen-specific IgA antibodies, but low levels of SIgA. Furthermore, high levels of SIgA seemed to protect sensitized children from developing allergic symptoms during the first 2 years of life, supporting a possible protective role of SIgA against development of allergy.

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.