Lymphoid cells in afferent and efferent intestinal lymph: lymphocyte subpopulations and cell migration.

Gut wall emigrating cells have been characterized in the intestinal lymph. The intestinal lymph duct was cannulated in 6-month-old minipigs. Under non-restraining conditions the efferent lymph from the mesenteric lymph nodes was collected in seven normal animals. Lymph coming directly from the gut (afferent lymph) was also collected in 18 pigs after resection of the mesenteric lymph node chains 3 months previously. The intestinal lymph flow was similar in both groups (around 18 ml/h). The lymphoid cell yield was 1.2 +/- 1.0 x 10(6)/h in control animals, while in mesenteric lymph node resected pigs it was around 20 times higher (26.2 +/- 17.6 x 10(6)/h). In the gut-derived lymph 76.5 +/- 8.8% T lymphocytes were observed (CD4+, 48.1 +/- 15.5%; CD8+, 53.6 +/- 12.7%). The percentage of immunoglobulin-positive cells was lower (IgM+, 10.1 +/- 4.5; IgA+, 1.7 +/- 1.1). In 14 mesenteric lymph node resected pigs a mean of 5.6 +/- 3.1 x 10(8) lymphocytes from the gut lymph were labelled in vitro with a fluorescent dye and retransfused. The labelling index of fluorescent cells in the intestinal lymph increased rapidly and remained at a high level until 44 h after cell transfusion. A four-to-ten times lower labelling index was found in the spleen, various lymph nodes and Peyer's patches. Most of the recovered lymphocytes were T cells. This model provides access to the cell pool leaving the gut wall, thus allowing an examination of its role in the gastrointestinal tract and other mucosal-lined organs.