Small intestinal epithelial cell kinetics and protozoal infection in mice

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The effects of chronic protozoal infection on small intestinal architecture have been examined in mice, infected with Giardia muris and Hexamita muris. Techniques used were conventional histology, quantitation of intraepithelial lymphocytes, microdissection and measurement of individual villi and crypts, and epithelial cell kinetic studies. The histology of small intestine from infected mice appeared normal apart from the intraepithelial lymphocyte numbers. Mean intraepithelial lymphocyte counts in two groups of uninfected mice were 11.6 and 13.6 per 100 epithelial cells, and in two groups of infected mice were 17.6 and 21.8. Dynamic studies showed that protozoal infection doubled the cell production per crypt per hour from mean values of 6.2, 7.3, and 8.2 in three groups of uninfected animals, to 11.8, 13.4, and 17.1 in groups of chronically infected mice. Cell production per villus was also influenced by protozoal infection, with values of 93, 99, and 101 cells per hr in groups of uninfected animals whereas in infected mice the values were 155, 162, and 180 cells per hr. Although there was no reduction in villus height in the infected animals, radioautography using [3H]thymidine confirmed that the enterocytes moved more rapidly up the sides of the villi than was the case for uninfected mice.