Non-random migration of CD4+, CD8+, gamma delta + T19+, and B cells between blood and lymph draining ileal and prescapular lymph nodes in the sheep fetus.

We have examined the circulation of CD5+, CD4+, CD8+, gamma delta + T19+, and B cells through ileal and prescapular lymph nodes in the sheep fetus in an environment uninfluenced by foreign antigen and ongoing immune responses or circulating immunoglobulins, and have contrasted this circulation with that occurring through the same tissue in 1-year-old sheep. The vast majority of lymphocytes circulating through fetal prescapular lymph nodes and fetal ileal lymph were T cells; however, there was a significantly higher concentration of B cells in ileal lymph compared to prescapular lymph. Furthermore, in contrast to 1-year-old sheep, there was an imbalance in the distribution of CD4+ cells and CD8+ cells in fetal prescapular and ileal lymph, with CD4+ cells enriched in prescapular lymph relative to other T cell subsets and CD8+ cells enriched in ileal lymph. Our results suggest that in the fetus either there is preferential migration of CD4+ cells through peripheral lymph nodes and/or CD8+ lymphocytes through the ileal gut, or newly formed CD8+ lymphocytes are being released from the ileum or ileal lymph node directly into ileal lymph.