Mesh:Child Mesh:Immunoglobulin E/immunology Mesh:Immunoglobulin A/blood Mesh:Food Hypersensitivity/immunology* Mesh:Food Hypersensitivity/blood* Mesh:Preschool Mesh:Food Hypersensitivity/diagnosis Mesh:Immunoglobulin A Mesh:Secretory/immunology Mesh:Immunologic Memory Mesh:Immunoglobulin E/blood Mesh:Humans Mesh:Male Mesh:Immunoglobulin A/immunology* Mesh:Adolescent Mesh:Age Factors Mesh:B-Lymphocyte Subsets/immunology Mesh:B-Lymphocyte Subsets/metabolism Mesh:Biomarkers Mesh:CD4 Lymphocyte Count Mesh:Female Mesh:Immunophenotyping Mesh:Infant Mesh:Liver Transplantation*/adverse effects Mesh:T-Lymphocytes Mesh:Helper-Inducer/immunology* Mesh:Helper-Inducer/metabolism food allergy immunoglobulin A polymeric IgA children secretory IgA specific IgA T follicular helper cells liver transplantation regulatory T cells