Although CD117 is primarily a marker for non-lymphoid progenitor, it has been reported to be detected on early lymphoid progenitor. CD117 expression has been found on a small subset of resting NK cells (CD56 bright), and about 30% of immature CD3–/CD4–/CD8– thymocytes. CD117 is also expressed on mast cells and detected on non-hematopoietic cells such as reproductive system, melanocytes and embryonic brain. Although CD117 is primarily a marker for non-lymphoid progenitor, it has been reported to be detected on early lymphoid progenitor. CD117 expression has been found on a small subset of resting NK cells (CD56 bright), and about 30% of immature CD3–/CD4–/CD8– thymocytes. CD117 is also expressed on mast cells and detected on non-hematopoietic cells such as reproductive system, melanocytes and embryonic brain.