Characterization of T cell epitopes in alphas1-casein in cow's milk allergic, atopic and non-atopic children.
BACKGROUND
One to two percent of infants suffer from IgE-mediated allergic reactions against cow's milk proteins. Most children develop clinical tolerance, but approximately 15% are still allergic by the age of 10 years. Little is known about the T cell epitopes in individual cow's milk protein in relation to allergy and tolerance.


OBJECTIVE
To identify T cell epitopes in alphas1-casein, the most abundant milk protein, and to investigate T cell responses toward these epitopes in allergic, atopic and non-atopic children.


METHODS
Allergen-specific T cell lines (TCLs) were derived from peripheral blood mononuclear cells of 11 cow's milk allergic, nine atopic and nine non-atopic children. T cell responses were measured to alphas1-casein and to overlapping peptides (18-mers), spanning the alphas1-casein molecule. Proliferation was determined by incorporation of (3)H-thymidine, and cytokine production (IL-10, IL-13 and IFN-gamma) was measured by ELISA.


RESULTS
Four main regions (amino acid (AA) residues 43-66, 73-96, 91-114 and 127-180) in the alphas1-casein molecule were immunogenic to T cells, among which the AA residues 133-156 spanned the immunodominant part. Only subtle differences were found in peptide recognition between the subject groups. Some of the peptides induced slightly Th1- or Th2-skewed cytokine responses. The increased levels of IL-10 in response to alphas1-casein observed in TCLs from atopic children appeared not to be linked to recognition of specific IL-10-inducing epitopes.


CONCLUSIONS
The immunodominant sequence in alphas1-casein is spanned by AA residues 133-156. Tolerance towards alphas1-casein in atopic children may be mediated by an overall induction of IL-10 and not by recognition of certain T cell epitopes. The identified T cell epitopes in children with cow's milk allergy may be useful targets in developing peptide immunotherapy.
Ruiter
B
B
Department of Dermatology/Allergology, University Medical Center, Utrecht, The Netherlands.
Trégoat
V
V
M'rabet
L
L
Garssen
J
J
Bruijnzeel-Koomen
C A F M
CA
Knol
E F
EF
Hoffen
E
E
D000293:Adolescent; D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D049109:Cell Proliferation; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000096:biosynthesis; D004311:Double-Blind Method; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology; D007108:Immune Tolerance; D016056:Immunodominant Epitopes / Q000276:immunology; D007223:Infant; D008213:Lymphocyte Activation / Q000276:immunology; D008892:Milk / Q000276:immunology; D016269:Milk Hypersensitivity / Q000276:immunology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology
D002364:Caseins; D016207:Cytokines; D018984:Epitopes, T-Lymphocyte; D016056:Immunodominant Epitopes; D010446:Peptide Fragments