METHODS: PBMC from 13 cockroach allergic donors were expanded in vitro with twelve different batches of German cockroach extract. After culture expansion, cells were re-stimulated with the different extracts and T cell responses were assessed by FluoroSpot (IL-5, IFNγ and IL-10 production). In parallel to the extracts, single allergen peptide pools for Bla g 1, 2, 4, 5 and 11 were tested to determine allergen immunodominance.
RESULTS: Dramatic variations in T cell reactivity were observed to the different cockroach extract batches. Response magnitudes varied over 3 logs within a single donor. While each donor presented a unique hierarchy of immunodominance for the 12 extracts tested, commercial batches produced for clinical use performed the most consistently. In-house extracts made from feces were significantly less potent in eliciting T cell responses than commercial extract made from whole body. Interestingly, no correlation between T cells and IgE reactivity (Glesner et al.) was observed.
CONCLUSIONS: Immunogenicity at the T cell level is highly variable between different cockroach extract batches. Different donors exhibit different response patterns, potentially dependent on their sensitization pattern. These finding have dramatic implications for the selection of potent extracts used for diagnostic purposes or allergen-specific immunotherapy.