A possible role of chemotaxis in germinal center formation.

During the germinal center (GC) reaction a characteristic morphology is developed. In the framework of a recently developed space-time model for the GC, a mechanism for the formation of dark and light zones has been proposed. There, the mechanism is based on a diffusing differentiation signal which is distinguished by follicular dendritic cells (FDC). Here, we investigate a possible influence of recently found chemoattractants on GC formation in the framework of a single cell-based stochastic and discrete three-dimensional model. This necessitates a more detailed spatial description. The model is enlarged by a detailed prescription of cell motility and it is introduced as a consistent volume concept. We consider various possible chemotactic pathways that may play a role for the development of both zones. Our results suggest that the centrocyte motility resulting from a FDC-derived chemoattractant has to exceed a lower limit to allow the separation of centroblasts and centrocytes. In contrast to light microscopy, the dark zone is ring shaped. This suggests that FDC-derived chemoattractants alone cannot explain the typical GC morphology.