Spatiotemporal dynamics of calcium signaling and metabolism in germinal center B cells
As the site of affinity maturation of the humoral immune response, the germinal center is an important check point for deciding the fate of B cells in the secondary lymphoid organs. Germinal centers represent spatially strictly organized microenvironments. This ensures a separation between antigen-induced B cell receptor activation and cell selection on the one hand, and B cell division associated with somatic hypermutation on the other. The cellular exchange between the two compartments of the germinal center is highly dynamic. Furthermore, it is known that activation of the B cell receptor induces profound changes in B cell metabolism. We hypothesize that this triggers a "metabolic clock" that sets a time window in which the B cells must receive a second signal to survive, for example T cell help. Intravital microscopy has contributed significantly to our understanding of germinal center dynamics in recent years. However, neither the mechanisms of spatiotemporal regulation at the interface between B cell receptor signaling and metabolism in the germinal center, nor the consequences for B cell selection, proliferation and differentiation are well understood. This is in part due to the lack of methods to analyze B cell metabolism and function at the single cell level in vivo. Using our unique imaging techniques, we aim to (i) determine the relationship between cytoplasmic calcium and general metabolic activity in germinal center B cells in vivo, (ii) assess how NAD(P)H-dependent metabolic pathways, specifically NADPH oxidases that produce reactive oxygen species, are involved in selection events in the germinal center, and (iii) define the effects of the metabolic microenvironment within the different germinal center zones on B cell activation. This project will provide for the first time correlative data on calcium signaling and metabolic activity of germinal center B cells in vivo, and elucidate the effects of the microenvironment on the interplay of B cell receptor signaling and metabolism under physiological conditions. Within the research group, we will benefit from the excellent environment and expertise in B cell metabolism and signaling. This complements our expertise in metabolic and functional imaging of B cells in the germinal center in vivo, which we will make available to the members of the consortium.
https://www.drfz.de/forschung/pb1/ag/immundynamik/
https://www.drfz.de/forschung/pb1/ag/biophysikalische-analytik/