DOK2 and leukemia: In the steady state, deletion of Dok2 (a known tyrosine downstream of CD200R signaling) has been associated with leukemia and expansion of hematopoietic stem cells.26 However, CD200-deficient mice are not characterized by expansion of BM progenitors in the steady state.27 This indicates that CD200 deletion per se is not sufficient to induce changes in myelopoiesis.