Gene-knock-out studies implicate roles of lymphotoxin (LT) alphabeta and LT betaR in the initial phase of Peyer's patch (PP) organogenesis. We recently identified the requirement of IL-7R alpha/gamma c/Jak3 signal in LT alphabeta production of IL-7R alpha+ cells. These observations lead us to a hypothetical model for PP organogenesis with three cellular components. The first is the producer of the ligand for IL-7R alpha, which then stimulate the IL-7R alpha+ cells to produce LT alphabeta activating the LT betaR+ cells to form an organizing center for PP organogenesis. This model is similar to that of inflammation, suggesting that PP organogenesis is a programmed version of inflammation.