The hematopoietic system is responsible for producing all of the body's blood cells and does so at an astounding pace. The modulation of hematopoiesis is predicated upon the interactions of circulating blood cells with small proteins called cytokines that perform various regulatory tasks, including controlling blood cell production. Cytokines have a variety of overlapping functions thereby supplying the hematopoietic system with a high degree of robustness. Serious pathologies can be induced by disruptions to even a single hematopoietic control loop; however, the overlaps in cytokine functions generally ensure that the cytokine paradigm operates without fail in the majority of people. Although many of the feedback mechanisms within the hematopoietic system have been intensively studied, there are still a large number of gaps in our characterization of hematopoietic controls.

In this talk, I will describe in two parts a physiological, delay differential equation approach to modelling hematopoiesis with the goal of untangling the complex interactions of blood cell production. I will discuss the control of neutrophil production by granulocyte colony-stimulating factor (G-CSF) and how we can exploit their physiological interplay to understand the mechanisms responsible for clearing G-CSF from the body in addition to pinpointing the half-removal time of neutrophils from the circulation. Similarly, I will address the regulation of megakaryocyte/platelet production by thrombopoietin and explore the dysregulation of this system in individuals with cyclical thrombopoiesis.