Immunoresponsiveness of Newborn Piglets and Peptidoglycan Derived from Bifidobacteria

Since the active immunoresponsiveness of neonates, including human babies and animals, is not well developed, passive immunity is acquired from the dam in the form of antibody via the placenta or with sucking colostrum. It is well known that piglets less than four weeks old are immunodeficient (1, 4, 14, 31, 35). The poor immunoresponse of the intestinal mucosa of piglets in this period is responsible for various local infections especially colibacillosis and viral diarrhea despite the presence of a large amount of immunoglobulin (Ig) in colostrum. This immunodeficiency of neonatal piglets seems to be analogous to the human babies' common variable hypogammaglobulinemia with B lymphocyte (10, 16). Though neonatal piglets are immunologically competent and respond to various antigenic stimulation, such as sheep blood cells and actinophage, the uncommitted multipotent immunocompetent cells are dominant (14). Since at this stage, monopotent (monoclonal) immunocompetent cells and memory cells are unable to develop, nor are the plasma cells able to mature, the secondary immune response and the producing ability of Ig are poor (3, 15). In newborn animals, there are very few plasma, cells in the lamina propria of the small intestines, and lymphoid follicles are poorly defined. These findings have also been proved by histological observation (9). In this context, the investigation has been carried out as follows; (1) analysis of immunoresponses in piglets of suckling stage, (2) serum concentration and properties of afetoprotein and serum level of albumin, and (3) influence of immunopotentiator on suckling piglets from the viewpoint of immunoresponse.