SELECTIVE LABELING OF MESENTERIC LYMPH-NODES - CELL PRODUCTION AND EMIGRATION OF NEWLY FORMED LYMPHOCYTES TO OTHER ORGANS

Lymphocyte production by mesenteric lymph nodes of normal young pigs was studied by intranodal injections of tritiated thymidine or tritiated deoxycytidine as DNA precursors. One or 2 days after selective labeling of mesenteric lymph nodes the relative and absolute number of lymphocytes derived from mesenteric lymph nodes were determined autoradiographically in the following organs: mesenteric, cervical and inguinal lymph nodes, spleen, thymus, bone marrow, Peyer''s patches, tonsil, different regions of the gut, lung and liver. Overall cell production of mesenteric lymph nodes, as derived from the sum of all labeled cells 1 day after labeling, was estimated to be 7 .times. 109 lymphocytes. Up to 40% of all newly formed lymphocytes had already left the lymph nodes within 1 day and were found in all organs studied. There was preferential homing to the mucosa of the small intestine, but a considerable number migrated to the spleen and even to the thymus and bone marrow. In lymphoid organs all labeled cells were small and medium-sized lymphocytes 1 and 2 days after labeling. In cervical lymph nodes, spleen, tonsil and Peyer''s patches the relative distribution to T [thymus-derived] and B [bone marrow-derived] cell areas was determined. There was obvious preference of newly formed lymph node cells to home to T cell areas. Labeling differences between thymidine or deoxycytidine were surprisingly low.