Identification of β-lactoglobulin-derived peptides and class II HLA molecules recognized by T cells from patients with milk allergy

Background Cow's milk allergy impairs the health and development of many infants since it deprives them of adequate nutrition. Cow's milk fractions contain many allergens, and β‐lactoglobulin (BLG) is one of the major allergens. Objective The purpose of this study was to determine T cell epitopes, antigen‐presenting molecules and cytokine production by T cells in relation to BLG. The results can provide new therapeutic possibilities of using analogue peptides of BLG for infants with cow's milk allergy. Methods Using a mixture of a panel of overlapping synthetic peptides that cover the entire BLG molecule, we established polyclonal BLG‐specific short‐term T cell lines and clones from peripheral blood mononuclear cells of four patients with allergy to cow's milk carrying most of the common human leucocyte antigen (HLA) haplotypes seen in the Japanese population. We then identified the T cell epitopes and antigen‐presenting molecules, and measured the production of cytokines interleukin (IL)‐4, IL‐5 and interferon‐γ in the culture supernatants. Results The T cell lines established from the four patients responded to seven different peptides. Three of the peptides stimulated the T cells of two donors, regardless of the HLA types. The patterns of inhibition of the proliferative responses of the cell lines by anti‐HLA class II antibodies were heterogeneous; three were mainly inhibited by anti‐HLA‐DR mAbs, and the other was inhibited by anti‐HLA‐DQ mAbs. High levels of IL‐5 were produced by these T cell lines. Conclusions Patients' T cells recognized BLG in association with a variety of HLA‐DR or ‐DQ as antigen‐presenting molecules. Although some peptides did have a more potent T cell stimulatory activity than others, the T cell receptor ligands formed with the BLG molecule are heterogeneous. Peptides for the desensitization of T cells of the patients with cow’s milk allergy need to be designed keeping in mind the different requirements in different ethnic groups.