Peanut Specific-CD4+ T Cells Responses in Peanut Allergic and Peanut Sensitized but Tolerant Subjects

The immunogenicity of different Ara h components in eliciting specific CD4 T cell responses in both peanut allergic and peanut sensitized but tolerant subjects (i.e. presence of peanut specific IgE but non-reactive to peanut food challenge) remains unclear. Fourteen allergic and six tolerance subjects were recruited. T cell responses toward Ara h 1, 2, 3, 6 and 8 were evaluated by CD154 up-regulation assays. T cell responses towards Ara h 2 were also evaluated by tetramer staining assay. T cell responses against Ara h 1, 2, 3 and 6 were significantly stronger compared to response against Ara h 8 in allergic subjects. Phenotypes of Ara h 2- and Ara h 1, 3, 6-specific-T cells were heterogeneous and could be CCR4+CD27-CRTH2+, CCR4+CD27+CCR6+ or CCR4+CD27+CCR6-. Experiments with both CD154 up-regulation and tetramers staining assay in evaluating Ara h 2 responses gave similar outcomes. Peanut-sensitized but tolerance subjects had significantly lower frequencies of Ara h 2 and Ara h, 1, 3, 6-sepcific T cells compared to allergic subjects. Ara h 8-specific responses in most subjects of this group were very weak or absence. Specific memory CD4 T cell response with a predominant TH2 phenotype against Ara h 1, 2, 3 and 6, but not against Ara h 8, was related to an allergic response. Conversely, a weak or an absence of a specific memory CD4 T cell response against Ara h 1, 2, 3 and 6 was related to an absence of a clinical response in peanut sensitized but tolerant subjects.