For a brief period during fetal lymph node organogenesis in mice, lymph node postcapillary high endothelial venules surprisingly express the Peyer's patch addressin MAdCAM-1. This expression allows initial seeding of this incipient structure by two unusual lymphocyte populations selectively expressing the Peyer's patch homing receptor integrin α4β7:CD4+CD3- oligoline-age progenitors and TCR γδ+ T cells. We show here that CD4+CD3- cells are lineage-restricted progenitors that express surface lymphotoxin-β (LTβ) and the chemokine receptor BLR1 and that can become natural killer cells, dendritic antigen-presenting cells, and follicular cells of unknown outcome, but these cells do not become T or B lymphocytes. Since the necessity of lymphotoxin in lymphoid organ development has been shown, we propose that the novel subset of CD4+ CD3-LTβ+ fetal cells is instrumental in the development of lymphoid tissue architecture.
Mebius, R. E., Rennert, P., & Weissman, I. L. (1997). Developing lymph nodes collect CD4+CD3- LTβ+ cells that can differentiate to APC, NK cells, and follicular cells but not T or B cells. Immunity, 7(4), 493–504. https://doi.org/10.1016/S1074-7613(00)80371-4