The porcine gastrointestinal lamina propria: an appropriate target for mucosal immunisation?

During the course of a lifetime, it has been calculated that we may consume between 100 and 700 tons of food. For the average British citizen, this is likely to include some 550 poultry, 36 pigs, 36 sheep, eight oxen, 10 000 eggs and dairy products (milk. butter cheese, etc.) equivalent to 18 tonnes of milk. As if that were not sufficient enough a challenge, the homeostasi s within the intestine is further complicated by the presence of 10(5)-10(1 1) bacteria (pathogenic and non-pathogenic) per gram of mucus and the const ant turnover of gut epithelial cells. Given such a magnitude of challenge, which, at least in health is heavily biased in favour of harmless antigens, it can be reasonably hypothesised that the default response of the intesti nal mucosal immune system would appear to be set heavily in favour of non-r esponsiveness and oral tolerance. The purpose of this review is to briefly describe recent progress from studies of the pig that support this hypothes is and to discuss the implications for future mucosal vaccine design. (C) 2 000 Elsevier Science B.V. All rights reserved.