After passive immunization of pregnant swine 24 and 48 hours before delivery with isolated fraction of 7S gamma globulin or with the whole serum of a high titer of antibodies to diphtheria and tetanus toxoid no traces of antibodies were detectedin newborn piglets by passive hemagglutination even if the globulin fraction of their sera was many times concentrated.
The effect of antibodies in the intestinal tract was studied in germ-free baby pigs whoso intestinal barrier was closed to macromolecules by the peroral administration of modified cow's milk for the first 72 hours after birth. They were then all contaminated with the pathogenic strain Escherichia cell 055 in amounts of 10' bacterial cells pcr animal. The controls, which were not given any antibodies, all died within 24 hours. All the experimental animals given 12.5--50 ml immune colostrum or serum survived, while of those given 50 ml normal serum or colostrum containing natural antibodies reacting with the Escherichia cell test strain, 50~ survived. ~'o circulating antibodies were found in the serum of the experimental animals after the administration of ~rum or colostrum. The antibodies present in colostrum thus appear to protect the newborn organism directly in the intestinal tract, which is the first site of bacterial invasion, as well as after infiltration into the blood stream.
Due to its close physiological and morphological resemblance to man, the pig occupies an important position in biomedical research. The minipig lends itself particularly well to germfree research. It is easy to deliver, maintain, and utilize in isolators. The colostrum-free, newborn germfree piglet lacking passively obtained antibodies is of an exclusive use if distinguishing the factors of natural and adaptive immunity is needed. It fits also well in studies investigating the earliest mechanisms of antibody synthesis. Under germfree conditions, the pig has been proved an excellent model for testing the action of ionizing radiation as well as of selected bacterial strains when monoassociated. Recently, conventional pigs have been used also for studies in total or selective decontamination of the intestinal tract by antibiotics and strict isolation.
Fundamental hematological and immunological data were obtained on sexually mature germfree miniature pigs fed, after the milk diet period, with cereal-type diet sterilized by gamma-radiation, and were compared with data of control conventional animals. Germfree adult pigs had a lower count of peripheral blood leukocytes with a lower percentage of neutrophil granulocytes and without any younger forms, a lower total serum protein level with a negligible amount of gamma and alpha 2 globulin fractions and a higher serum albumin and beta globulin level. In the mesenteric lymph nodes and in spleen, surface IgA-bearing cells predominated over surface IgG-bearing cells. Also a large amount of IgA-containing cells was found in the intestinal lamina propria, where the IgG cells were present in a negligible amount. IgM cells were the most frequent surface isotype in peripheral blood. The count of blood T lymphocytes was more than doubled.
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