Intestinal cryptopatch formation in mice requires lymphotoxin α and the lymphotoxin β receptor

Interactions between lymphotoxin (LT)alpha(1)beta(2) on inducer cells and the lymphotoxin beta receptor (LTbetaR) on stromal cells initiate development of lymph nodes and Peyer's patches. In this study, we assessed the contributions of LTalpha and LTbetaR to the development of cryptopatches (CP), aggregates of T cell precursors in the mouse small intestine. Mice genetically deficient in LTalpha or LTbetaR lacked CP. Bone marrow from LTalpha-deficient mice was unable to initiate development of CP or isolated lymphoid follicles (ILF) after transfer to CDbeta2-null mice lacking CP and ILF. However, LTalpha-deficient bone marrow-derived cells contributed to CP formed in CDbeta2-null mice receiving a mixture of wild-type and LTalpha-deficient bone marrow cells. Transfer of wild-type bone marrow into irradiated LTalpha-deficient mice resulted in reconstitution of both CP and ILF. However, the LT-dependent formation of CP was distinguished from the LT-dependent formation of ILF and Peyer's patches by not requiring the presence of an intact NF-kappaB-inducing kinase gene. CP but not ILF were present in the small intestine from NF-kappaB-inducing kinase-deficient alymphoplasia mice, indicating that the alternate NF-kappaB activation pathway required for other types of LTbetaR-dependent lymphoid organogenesis is dispensable for CP development. In addition, we identified VCAM-(1+) cells within both CP and ILF that are candidates for the stromal cells involved in receiving LT-dependent signals from the hemopoietic precursors recruited to CP. These findings demonstrate that interactions between cells expressing LTalpha(1)beta(2) and LTbetaR are a shared feature in the development of all small intestinal lymphoid aggregates.