It is well established that allergy development can be prevented by repeated low-dose exposure to contact allergens. Exactly which immune mechanisms are responsible for this so-called low zone tolerance (LZT) is not clear, although CD8+ suppressor T cells are known to have a role. Here, we show that TNF released by tolerogenic CD11+CD8+ DCs located in skin-draining lymph nodes is required and sufficient for development of tolerance to contact allergens in mice. DC-derived TNF protected mice from contact allergy by inducing apoptosis in allergen-specific effector CD8+ T cells via TNF receptor 2 but did not contribute to the generation and function of the regulatory T cells associated with LZT. The TNF-mediated killing mechanism was induced in an allergen-specific manner. Activation of tolerogenic DCs by LZT CD8+ suppressor T cells and enhanced TNF receptor 2 expression on contact allergen–specific CD8+ effector T cells were required for LZT. Our findings may explain how tolerance protects from allergic diseases, which could allow for the development of new strategies for allergy prevention.
Ulrike Luckey, Marcus Maurer, Talkea Schmidt, Nadine Lorenz, Beate Seebach, Martin Metz, Kerstin Steinbrink
CD8+ DCs are the critical source for TNF in LZT.