Schematic representation of the model concept for a chimeric situation. Cellular development within the stem cell compartment (left) is characterized by the possibility of individual cells (black and white circles) to reside in 2 different growth environments (GE-A, gray; GE-Ω, white). The affinity (a) of cells to reside in GE-A can reversibly change depending on the actual GE (gain in GE-A, loss in GE-Ω). The processes of a-loss/gain and of transition between the 2 growth environments (characterized by the model parameters d, r, and f_α, f_ω, respectively) are assumed to be strain specific, illustrated by the D2/B6 superscripts. The same holds for the process of proliferation (amplification due to cell division), which is described by the average generation time τ_c. Cells that have lost the potential to change to GE-A and, therefore to regain a (denoted as differentiated cells), will pass through different precursor stages to become mature leukocytes. Regulation processes of precursor and mature cell stages are neglected in the current model version.