Probiotics and lung immune responses.

There is increasing interest in the potential for microbe-based therapeutic approaches to asthma and respiratory infection. However, to date, clinical trials of probiotics in the treatment of respiratory disease have met with limited success. It is becoming clear that to identify the true therapeutic potential of microbes we must move away from a purely empirical approach to clinical trials and adopt knowledge-based selection of candidate probiotics strains, dose, and means of administration. Animal models have played a key role in the identification of mechanisms underlying the immunomodulatory capacity of specific bacteria. Microbe-induced changes in dendritic cell phenotype and function appear key to orchestrating the multiple pathways, involving inter alia, T cells, natural killer cells, and alveolar macrophages, associated with the protective effect of probiotics. Moving forward, the development of knowledge-based strategies for microbe-based therapeutics in respiratory disease will be aided by greater understanding of how specific bacterial structural motifs activate unique combinations of pattern recognition receptors on dendritic cells and thus direct desired immune responses.