I t has been shown by Gowans and Knight (1) that when small lymphocytes obtained from rat thoracic duct lymph are injected intravenously into other rats, the ceils rapidly "home" to lymphoid tissue, that is, to the white pulp of the spleen, lymph nodes in all locations, and lymphoid tissue of the gut, including Peyer's patches. There is considerable evidence that this process is physiological, ...

Development of lymphoid tissue is determined by interactions between stromal lymphoid tissue organiser (LTo) and hematopoietic lymphoid tissue inducer (LTi) cells. A failure for LTo to receive appropriate activating signals during embryogenesis through lymphotoxin engagement leads to a complete cessation of lymph node (LN) and Peyer's patch development, identifying LTo as a key stromal populati...