Non-random distribution of intraepithelial lymphoid cells in follicle-associated epithelium of Peyer's patches in mice.

The spatial distribution of intraepithelial lymphoid cells in follicle-associated and villus epithelium within Peyer's patches was studied quantitatively in Balb/C and CFW/L1 mice. The results were essentially the same for both strains. The distribution of the number of lymphoid cells per segmental length (equal to an average width of an epithelial cell) of dome epithelium was found to be non-random, since it deviated significantly from the theoretical Poisson distribution. Some segments of the dome epithelium, therefore, are lymphocyte-rich and some are lymphocyte-depleted, i.e. they contain either more, or less lymphoid cells than expected from the random distribution. This was in contrast to the distribution in the epithelial layer of the villi, in which the distribution of the number of lymphoid cells per segment followed the Poisson distribution. It was also demonstrated that segments rich in lymphocytes in the dome epithelium occurred in series or clusters. Lymphoid cell clustering was not observed in the villus epithelium. Possible mechanisms responsible for the non-random spatial distribution of lymphoid cells within the dome epithelium of the mouse Peyer's patches are discussed.