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Transplantation of the "presumptive" Peyer's patch of fetus or newborn mice under the kidney capsule of adult syngeneic recipient.

Small fragments of caecum from fetus, newborn or several-day-old mice were transplanted under the kidney capsule of adult syngeneic hosts. Transplants were derived from such a part of caecum at which in adult mice a Peyer's patch is always present (experimental group) or from such a part at which Peyer's patch is never located (control group). Donors were chosen from such early developmental stage at which Peyer's patches not yet been formed, hoping to observe Peyer's patch formation in transplants in view of possible influence of intestinal epithelium on a lymphocyte homing. After 10 to 150 days, transplants were asessed histologically. None Peyer's patche was formed. However, small accumulations of lymphoid cells were located in vicinity of epithelial cysts and blood vessels occasionally filled with lymphocytes were seen in the experimental but not in control group. The results showed that either number of epithelial cells or degree of their specialization were unsufficient for Peyer's patch formation. Other factors like the antigenic stimulation from the gut lumen might be thus necessary for Peyer's patch development.