Development of immune responses in early pig ontogeny.

Low amounts of immunoglobulins, produced without any known cause of stimulation, can be detected in sera and cells of fetal and colostrum deprived newborn pigs. These immunoglobulins are believed to represent the preimmune antibody repertoire on the basis of their polyspecificity and reactivity against self antigens. In vitro activation of liver and spleen cells with various polyclonal B cell activators (PBA) results in pronounced immunoglobulins synthesis as measured in the culture media by enzyme-linked immunosorbent assay. Intrauterine injection of fetal and germfree pigs with PBA led to increased IgM, IgG and IgA levels in sera. Specific responses during fetal development were studied after intrauterine immunization. Antibodies to the heapten and its carrier flagellin, could be detected 7 days after the immunization of 55-day-old fetuses. Fetal and colostrum germfree pigs may be useful experimental models in which developmental immunity can be studied in the absence of maternal antibodies and environmental antigens.