Long recognized as essential for proper lymph node organogenesis during fetal development, recent evidence has suggested that LTi cells also play an important role in the adult. Recent work from our laboratory has identified the previously unknown human LTi as lineagenegCD127+RORc+ cells. In vitro studies suggest a direct relationship of LTi cells with CD127+RORc+ NK cells. Both LTi and CD127+ NK cells isolated from human tonsil produce IL-22, IL-17, TNFalpha, and lymphotoxin, but not IFNgamma. LTi cells are present in a low frequency in human tonsils, thus making detailed analysis challenging. Using a rigorous selection strategy, we have successfully purified LTi and CD127+ NK cells and expanded these cells 30-100 fold using a feeder cell mixture and IL-2. These expanded LTi and CD127+ NK cell lines maintain RORc expression and production of IL-22 and IL-17. Interestingly, following ex vivo expansion both LTi and CD127+ NK cells produce IFNgamma upon stimulation. An outstanding question remains the cytotoxic potential of LTi and CD127+ NK cells, which we can now investigate. Further, we are investigating the role of stimulatory cytokines in regulating IL-22 production from LTi and CD127+ NK cells. As aberrant regulation of IL-22 can contribute to inflammatory diseases, further understanding of this novel population of IL-22 producing cells is of great relevance.