The effects of T cell peptides in patients sensitive to cats

Summary Synthetic peptides representing T cell epitopes of the major cat allergen Fel d 1 were administered by intradermal injection or inhalation to cat allergic asthmatic volunteers. Both routes of administration were associated with the induction of IgE‐independent, MHC‐restricted isolated late asthmatic reactions (LAR; prolonged bronchoconstriction initiating 2–4 hours after peptide challenge) in a proportion of individuals. Administration via the intradermal, but not the inhaled route, was associated with the induction of antigen‐specific hyporesponsiveness or “tolerance”, both in vivo and in vitro . Following intradermal peptide administration, the magnitude of both the early‐ and late‐phase skin reaction to intradermal challenge with whole allergen extract were significantly reduced. In vitro, proliferative responses of peripheral blood mononuclear cells (PBMC) were reduced together with both Th1 and Th2 cytokines. Production of IL‐10 was increased. LAR were not a pre‐requisite for the induction of tolerance. Hyporesponsiveness was transient but several months were required to return to basal reactivity.