Background TSLP has been described as a “master TH2 cytokine” with pleiotropic effects. Recent research shows that TSLP can directly activate mast cells and CB CD34 hemopoietic progenitor cells (HPC), with release of TH2 cytokines/chemokines in a TSLP-dependent manner [1,2]. Additionally, TSLP may modulate the function of CD34 cells via changes in hemopoietic cytokine receptors (HCR), which are altered in CB CD34 cells of atopic at-risk infants [3]. In this study, we aimed to characterize HCR expression on CD34 cells and to examine CD34 cell differentiation following TSLP stimulation.