Abstract
An investigation into the occurrence of specific food antibodies in adults and infants has been carried out, and the levels of specific antibodies have been considered in relation to their significance in atopy and its development. Enzyme-linked immunosorbent assays (ELISA) were developed to determined specific antibodies to ovalbumin, gliadin and β-lactoglobulin in a number of biological fluids. A novel method for the quantification of specific antibodies in serum was developed. ELISAs were also developed to determine food antigens, ovalbumin and gliadin, in serum. A very wide range of specific circulatory IgG and salivary IgA antibodies to the three food proteins were observed in normal subjects. Specific anti-ovalbumin IgG levels were significantly higher than anti-gliadin (p<0.05) and anti-β-lactoglobulin IgG (p<0.01). Explanations are put forward for the observed differences in specific antibody titres to the food proteins investigated. In atopic subjects, specific anti-ovalbumin IgG levels were significantly higher than in non-atopic subjects (p<0.02). It is proposed that this difference is due to the hyper-responsiveness of atopic individuals combined with the antigenicity of ovalbumin. IgG subclass antibodies to ovalbumin and gliadin were found predominantly in the IgG4 subclass, with anti-β-lactoglobulin IgG distributed between IgG2, IgG3 and IgG4. The proportion of antibodies to ovalbumin and gliadin in the IgG3 subclass was significantly greater in the atopic subjects than in the non-atopic group (p<0.05, p<0.02 respectively). The possibility of a pathogenic role for specific IgG3 antibodies is discussed. Feeding studies were carried out to determine the uptake of food antigens from the gut. The uptake of antigenically viable ovalbumin appeared greater than that of gliadin, and the presence of gliadin was found to significantly reduce the uptake of ovalbumin (p<0.05). The concentrations of antigen measured was related to the level of specific antibodies, and the influence specific antibodies exert on antigen uptake and its determination is considered. A prospective study of 26 infants was carried out to investigate the effect the presence of maternal atopy and mode of feeding have on the production of specific antibodies in the infants, and the development of atopy. The presence of maternal atopy and whether the infant was bottle-or breast-fed had significant effects on the production of specific serum antibodies in the infant. Maternal specific antibody levels appear to influence production in the infant, and high maternal titres of anti-β-lactoglobulin IgG are related to the development of atopy in the infants. A model for the development of specific antibody titres in infants under the influence of maternal antibodies is put forward, and the importance of bottle and breast feeding, and maternal atopy discussed. The clinical implications of the findings of this project are discussed in relation to the prevention of atopy development in infants.