Allergen-specific Th2 responses in young children precede sensitization later in life.

Allergic sensitization is initiated by allergen-specific Th2-cell responses. Data on early allergen-specific T-cell responses in allergic children are scarce. We hypothesized that allergen-specific Th2-cell responses can be detected preceding sensitization. Therefore, peripheral blood mononuclear cells (PBMC) of nonsensitized, 'not-yet' sensitized or sensitized children were cultured with highly purified allergens. Cytokine levels in supernatant were determined using multiplex assay and GATA3 expression by flow cytometry. PBMC of sensitized children aged 3 and 5 years showed higher production of IL4, IL5 and IL13 and higher expression of GATA3 in response to purified allergens compared to nonsensitized children. PBMC of children that were 'not-yet' sensitized already showed higher levels of IL5 and IL13 and higher GATA3 expression at age 3 years. This shows that allergen-specific in vitro Th2 responses precede the detection of allergen-specific IgE, which can provide a window of opportunity for novel therapeutic interventions.