Lymph nodes, spleens, and Peyer's patches of germ-free mice are relatively inactive. The tissues are small and contain rare, small, indistinct, germinal zones. When exposed to antigenic stimuli (Salmonella paratyphi A and lymphocytic choriomeningitis virus), the tissues become larger and germinal zones appear coincident with antibodies in the blood. The Peyer's patches were activated if antigen was absorbed from the intestinal lumen into the circulation but not if the antigen was administered parenterally. There was no demonstrable immunological response by the germ-free mouse to Streptococcus faecalis.

No abstract

Prostate adenocarcinomas were induced in Lobund Wistar rats following subcutaneous implants of silastic chambers containing testosterone propionate. The tumors resembled those that developed spontaneously in the Lobund Wistar rats. Tumors were not induced in ACI rats by the same treatment schedule.

The effect of germ-free life and dietary restriction (DR) on life span and pathology was investigated in isolator housed germ-free (GF) and conventional (CV) Lobund-Wistar rats fed either ad libitum or restricted to 12 grams per day (70% of adult ad libitum intake) of a natural ingredient diet from weaning. The median length of life of ad libitum CV and GF rats was 31.0 and 33.6 months respectively, while DR increased the median length of life of CV and GF rats to 38.6 and 37.8 months respectively. DR reduced the frequency or postponed the occurrence of diseases which eventually lead to death in the Lobund-Wistar rat. This was especially true of prostate adenocarcinoma, prostatitis, and mammary fibroma. The reduced early food intake and smaller body weight of adult GF rats may be the reason ad libitum fed GF rats live slightly longer than their CV counterparts, but GF life was without additional effect on life span when food intake was restricted.

Over the course of 20 weeks, Sprague-Dawley rats developed intestinal tumors in response to an intraperitoneal injection of the acetate derivative of dimethylnitrosamine. The same agent did not induce tumors in Lobund-Wistar rats. The number of tumors was significantly smaller in rats given drinking water containing indomethacin (beginning 14 days after the injections) than in control rats given drug-free water.