Ontogeny of ovine lymphocytes. III. An immunohistological study on the development of T lymphocytes in sheep fetal lymph nodes.

The development of T lymphocytes in ovine fetal lymph nodes was studied immunohistologically using a panel of monoclonal antibodies. T lymphocyte subsets appeared within the ovine fetal lymph node in a specific sequence. SBU-T1- and SBU-T8-positive lymphocytes were seen at Day 47 of gestation. LCA, sIg, MHC I, MHC II, SBU-T6 and 46.66 antigens were also seen within the lymph node at this time. The first SBU-T4-positive cells were seen within the fetal lymph node at Day 50 of gestation, along with the first 20.96-, 25.69- and 38.38-positive cells. SBU-T19 lymphocytes appeared later in gestation, being present in fetal lymph nodes from Day 69 of gestation. The appearance and distribution of T and B cells in the developing lymph nodes of the ovine fetus is described and compared with the ontogeny of lymphocytes in the fetal thymus and spleen.