Hematopoiesis, the making of blood cells, is initiated via the binding of hematopoietic cytokines to specific receptors on the surface of hematopoietic stem cells. We will dissect the interactions of Flt3L and SCF, two essential cytokines, with their respective receptors using structural biology (x-ray crystallography) and bindingstudies (microcalorimetry and SPR). We hope to generate insights leading to the design of agonists with improved binding properties.