Newborn mammals are not born with an immune system that can protect them against pathogens they encounter, only the potential to develop such a system; this process is called adaptive immunity. Thus the neonatal period is the ?critical window? when such development occurs. The fact that it is also the period of highest mortality, indicates that development of this adaptive system: (a) may be suboptimal in some cases and (b) needs further investigation. For certain mammals, perhaps all birds and many lower vertebrates and prochordates, the lymphoid tissues involved at this stage appear to be associated with the hindgut. In pigs, these are called the ileal Peyer's patches (IPP) that are found in various hoofed mammals but not in rodents or humans. This is a proposal to support or reject the hypothesis that the IPP is crucial for the development of adaptive immunity in neonates. Approaches to testing this hypothesis include assessing the effect of removing the IPP; analyzing the antibody repertoire of IPP from germfree and colonized piglets at different ages; and characterizing the specificity of IgG3 antibodies that are postulated to develop at this stage independent of antigens and with a broad specificity. The study is a collaboration of investigators at four universities, two countries and one government laboratory. It has a training program component involving undergraduate internships and graduate student exchange.
