Regulatory CD4+ T cells in allergic asthma.

Active suppression by regulatory T cells (Tregs) appears to play a key role in the downregulation of T-cell responses to foreign antigens. Several subtypes of Tregs have been described but their mechanisms of action remain unclear. Recent data demonstrate that the suppressive capacity of natural Tregs could be associated with cytotoxicity due to the release of granzymes, which are capable of apoptosis induction in target effector T lymphocytes and in antigen-presenting cells, such as dendritic cells. The mechanism of such nonspecific Tregs is discussed. Peptide immunotherapy is thought to induce regulatory cells capable of suppressing autoimmune and allergic diseases. We have recently optimized a vaccination strategy by which cytotoxic antigen-specific adaptive Tregs can be elicited towards allergens involved in allergic asthma. Such a strategy could be of value in the treatment of allergic asthma.