In these studies the differential roles of LTalpha and LTalphabeta complex have been discussed with regard to development of lymphoid organs in ontogeny and in inflammation, LTalpha is necessary for PLNand MLN, most likely as both LTalpha and LTalphabeta complex, whereas only LTalphabeta is required for MLN. Both are involved in the cellularity of the NALT. When expressed as a transgene, LTa alone can induce cellular accumulation and MAdCAM, but not PNAd, an epitope associated with PLN HEV. These data suggest that LTalphabeta complex plays a crucial role in PNAd. One hypothesis is that LTalphabeta induces PNAd through modification via an HEV sulfotransferase. RIPLTalpha.RIPLTbeta mice will provide an important tool to investigate this question.