Use of interleukin 7 receptor-alpha knockout donor cells demonstrates the lymphoid independence of dendritic cells.

The precise lineage of dendritic cells (DCs), including skin Langerhans cells (LCs), is unclear. Interleukin 7 (IL-7) and its receptor (IL-7R alpha) are known to mediate lymphopoiesis, and IL-7 is also known to be essential for the generation of DCs from lymphoid-committed precursors in vitro. Thus, to determine the developmental lymphoid (or IL-7R alpha) dependency of various DCs and to examine the importance of IL-7/IL-7R alpha for DC development in vivo, we used IL-7R alpha knockout (KO) donor cells to reconstitute DCs/LCs in sublethally irradiated recipients and compared the results to those obtained using wild-type (WT) donor cells. We found that lymphoid lineage cells (except natural killer [NK] cells), including thymocytes, were less efficiently reconstituted by IL-7R alpha KO donor cells, whereas myeloid lineage cells and DCs/LCs were equally well reconstituted by both the IL-7R alpha KO and WT donor cells. Overall, we conclude that IL-7R alpha is not required for the development of DCs/LC in vivo.