The role of gut-associated lymphoid tissues in the generation of immunoglobulin-bearing lymphocytes in sheep.

Experiments were designed to examine the relative contributions of Peyer's patches and mesenteric lymph nodes to the population of circulating immunoglobulin-bearing lymphocytes in sheep. The ileum, with more than 90% of the total Peyer's patches, the mesenteric lymph nodes, or both, were removed from lambs at different stages of development and the composition of the cell populations in lymph from different sources and in the blood was examined. Lambs which had had the ileum removed before or within a few days of birth were deficient in small lymphocytes bearing membrane immunoglobulin. This deficit remained for at least the first year of the animals' lives. Neither the removal of mesenteric lymph nodes nor removal of the ileum had any statistically significant effect on the total output of cells or on the population of IgA-producing cells in lymph draining from the gut.