B and also T lymphocytes migrate via gut lymph to all lymphoid organs and the gut wall, but only IgA+ cells accumulate in the lamina propria of the intestinal mucosa

In pigs the lymphocytes emigrating from the intestinal wall were collected by cannulating the lymphatics, labeled in vitro using a fluorescent dye and retransfused. The injection of 6.6 +/- 4.2 x 10(6) cells resulted in a labeling index between 1.5 % in intestinal lymph, 0.2 % in the spleen and lymph nodes, similar to 0.1 % in the intestinal lamina propria and 0.003 % in intraepithelial lymphocytes. About 25 % of the injected cells were present in the blood and 1 % was recovered in the lymph. T cells were found in similar proportions in the injected and the recovered cells in the organs (70-80 %). The proportion of IgA(+) cells among the immigrated cells in the intestinal lamina propria ranged from 5 to 8 %, which in absolute numbers was up to 60 % of the injected IgA(+) cells. T and IgM(+) cells did not show a higher accumulation in any organ. These experiments in conventional, unrestrained animals revealed that (1)T cells immigrate into the intestinal lamina propria, (2) preferential migration of IgA(+) cells from gut lymph to the intestinal lamina propria is obvious under in vivo conditions and (3) the immigrated IgA(+) cells represent a very small population which is difficult to detect when analyzed in relative numbers.