SPECIFICITY OF THE HUMAN IGE RESPONSE TO THE DIFFERENT PURIFIED CASEINS IN ALLERGY TO COWS MILK-PROTEINS

Background: Cow's milk is one of the most frequent food allergens. Who le casein appears to be highly allergenic. It corresponds to an associ ation of four different proteins, alpha(s1), alpha(s2), beta- and kapp a-caseins in approximate proportions of 40, 10, 40, End 10%, respectiv ely. Methods: These different components were thus purified and used a s immobilized antigens in an original enzyme immunoassay to measure sp ecific serum IgE response in a population of 58 children (median age 1 1 months) allergic to cow's milk who were sensitive to whole casein. R esults: A great variability was observed in the affinity and specifici ty of specific IgE responses in milk-allergic patients' sera. 85% of t he patients presented IgE against each of the four caseins, Statistica lly higher amounts of specific IgE were found to be directed against t he most abundant fractions (alpha(s1)- and beta-casein). Co- and/or cr oss-sensitization to the different caseins were seen in most of the pa tients sensitive to whole casein. Conclusion: These results suggest th at both distinct and common epitopes may occur on these different case ins. The major site of phosphorylation which is the most conserved dom ain in three caseins could be involved in the IgE response to casein a nd in immunocross-reactivity between these proteins.