Characterization of thymic stromal-derived lymphopoietin (TSLP) in murine B cell development in vitro.

B cell development is dependent on both direct interactions with stromal cells and their secreted cytokines. The precise mechanisms by which these interactions regulate B cell differentiation are currently unknown. We report here that a novel growth factor thymic stromal-derived lymphopoietin (TSLP) can replace the activity of interleukin-7 (IL-7) in supporting B cell development in vitro. TSLP was found to promote the proliferation and differentiation of committed B220+ B cell progenitors from day 15 fetal liver. Phenotypic analysis of these cells revealed that they are at the pro-B cell stage of differentiation and express cell surface markers characteristic of pro-B cells cultured in IL-7. TSLP can replace the activity of IL-7 in supporting the progression of B lymphocytes from uncommitted bipotential precursors. In the absence of either TSLP or IL-7, the progeny of cells that give rise to mature B lymphocytes fail to develop from these bipotential precursors. Moreover, TSLP can substitute for IL-7 in supporting the sustained proliferative response exhibited by B cell progenitors from CBA/N mice. Together these results show that TSLP can replace the requirement for IL-7 during in vitro B cell development.