EFFECTS OF THE NORMAL MICROBIAL FLORA ON VARIOUS TISSUE ELEMENTS OF THE SMALL INTESTINE

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Abstract
Comparative studies in germfree and conventional chickens and rats have indicated that the presence of the normal intestinal flora augments the amount of lamina propria tissue in the wall of the small intestine. This effect was particularly accentuated in the "core of villus", i.e. in the portion of the lamina which extends into the villi. Other tissue elements of the intestinal wall did not appear to be particularly involved in this effect. Oral treatment of conventional chickens with penicillin at low levels from birth resulted in a reduction of the lamina propria which was qualitatively similar to the state observed in germfree animals. Clostridium perfringens or Streptococcus faecalis which, based on previous work were suspected to be among the prime stimulating elements of the intestinal flora in chickens, augmented the lamina propria when orally seeded into the animals at birth. Penicillin treatment of the monocontaminated animals reverted the lamina tissue to "germfree-like" status. A review of the data on lamina propria, RE cell count of the intestinal wall, serum gamma globulin and circulating antibodies, which were commonly observed in the animals of this series has indicated that various elements of the flora considerably differ in their stimulatory effect on the cellular and humoral defenses of the host. Bacterial species, population and perhaps metabolic state should be regarded as essential determining factors in this phenomenon.