The postnatal development of the mucosal immune system and mucosal tolerance in domestic animals

Abstract

-The mucosal immune system is exposed to a range of antigens associated with pathogens, to which it must mount active immune responses. However, it is also exposed to a large number of harmless antigens associated with food and with commensal microbial flora, to which expression of active, inflammatory immune responses to these antigens is undesirable. The mucosal immune system must contain machinery capable of evaluating the antigens to which it is exposed and mounting appropriate effector or regulatory responses. Since the immune system is likely to have evolved initially in mucosal tissues, the requirement to prevent damaging allergic responses must be at least as old as the adaptive immune system, and studies of the mechanisms should include a range of non-mammalian species. Despite the importance for rational design of vaccines and for control of allergic reactions, the mechanisms involved are still largely unclear. It is not clear that the classical experimental protocol of "oral tolerance" is, in fact, measuring a biologically important phenomenon, nor is it clear whether tolerance is regulated in the evolutionarily recent organised lymphoid tissue (the lymph nodes) or the more ancient, diffuse architecture in the intestine. The capacity of the immune system to discriminate between "dangerous" and "harmless" antigens appears to develop with age and exposure to microbial flora. Thus, the ability of an individual or a group of animals to correctly regulate mucosal immune responses will depend on age, genetics and on their microbial environment and history. Attempts to manipulate the mucosal immune system towards active immune responses by oral vaccines, or towards oral tolerance, are likely to be confounded by environmentally-induced variability between individuals and between groups of animals.

Immunoregulation: A Proposal for an Experimental Model

“…Several studies, including humans, swine and mice, demonstrated that small quantities of food proteins absorb intact across the intestinal epithelium in adults and neonates (Bailey et al, 1994;Telemo et al, 1991). Recent studies of the phenomenon of oral tolerance suggest that it is variable and age-dependent (Bailey & Haverson, 2006) as well as the present of commensal microbial flora in the intestine.…”

“…Theirs' APCs expressing MHC II protein class. Immature dendritic cells are present in large numbers within the villi and co-localise with T-cells expressing the CD4 coreceptor in the pig, but expressing the low affinity Fc RIII (Bailey & Haverson, 2006). The point is that diffuse mucosal tissue has the first role in immune regulation, rather than active defensive responses.…”

Intramuscular vaccination of young calves with aSalmonellaDublin metabolic-drift mutant provides superior protection to oral delivery

“…However, although some mechanisms of the host, such as the gastrointestinal mucosal barrier, are suggested to play an important role in host-pathogen interaction [1], it is still unclear how interaction between immunity and Salmonella at the site affect the induction of these inflammatory reactions. Furthermore, as the structure and components of the mucosal immune system in the gut of young animals differ from those of adult animals [5,22], host-pathogen interaction and subsequent clinical signs may vary greatly depending on the level of maturity of this immune system. The mechanisms involved in immunity in the most susceptible age group of calves may be very complex.…”

Antigenicidad de piensos y materias primas proteicas en conejos

“…La presencia de IgG frente a antígenos de la dieta también se ha estudiado en animales de producción, principalmente en lechones y terneros frente a la soja (Bailey y Haverson, 2006). Los problemas por el uso de soja se asocian a la presencia de factores antinutricionales y proteínas antigénicas como glicinina y β-conglicinina (Huisman y Jansman, 1991).…”

“…La antigenicidad de la harina de soja ha sido muy estudiada en lechones y terneros (Bailey y Haverson, 2006) y también se sabe que la utilización de guisante en piensos de iniciación de lechones provoca un aumento de IgG específicas en mucha mayor medida que la caseína (Salgado et al, 2002a). Por el contrario, no se ha encontrado información sobre la antigenicidad de la harina de girasol, probablemente por su escasa utilización en piensos para lechones y terneros (De Blas et al, 2010).…”