Mechanisms of oral tolerance: Dendritic cells summary of part II

The session included talks and a discussion period in which novel paradigms for the role of DCs in generating tolerance as well as immunity at mucosal surfaces were proposed. Presentations raised questions on the dichotomy of DC responses to safe or pathogenic antigens (FIG. 1). Drs. Kelsall's and Rescigno's presentations helped attendees appreciate key roles played by DC subsets in monitoring mucosal surfaces for danger signs derived from enteric flora, local immune cells, and, especially, epithelial cells. A novel, yet fundamental view of DCs as migratory cells was presented by Dr. MacPherson, who elegantly delineated the role of DCs in shuttling antigen between mucosal tissue and inductive sites within draining LNs. Dr. Viney's presentation challenged the audience to consider how DCs affect responding T cells. Her examination of essential enzymes (e.g., IDO) expressed by DCs enhanced our understanding of the biochemical basis of tolerance versus immunity. Work by Dr. Umetsu and others suggested that innovative approaches to genetic research carry the potential to reveal novel relationships between genotype and phenotype in human disease. Taken together, the session allowed attendees to engage an international panel of speakers at the cutting edge of DC biology. Paradigms developed from newly generated model systems were discussed between researchers and participating audience members. Such interactions may potentially affect a range of clinically relevant areas, from enhanced host defense to mucosal pathogens, to improved mucosal vaccine development, to the development of new therapies for autoimmune disorders such as asthma and inflammatory bowel disease.