differentiation of the common lymphoid progenitor

major organ of lymphopoiesis at embryonic stage and to some degree at the adult stage

a group of lymphatic follicles found in the lamina propria of the small intestine (ileum) extending into its submucosa

located symmetrically at various places in the body, are "customs barriers" for all "regional" antigens

their lymphocytes surround arterioles forming a cuff or so-called periarteriolar lymphoid sheaths

contains lobules separated by trabeculae