B Cell Activation Factor (BAFF) is an important cytokine in regulating B cell homeostasis through its high affinity BAFF receptor (BAFF-R). This pathway is known to mediate survival and maturation of B cells. However, the physiological role of BAFF-R signalling in regulating the germinal centre (GC) during antigen-specific B cell responses is yet to be fully understood. By studying the SWHEL system in conjunction with BAFF or BAFF-R deficient mice, we can dissect the role of BAFF-BAFF-R signalling in normal affinity-based selection in the GC in vivo. Our studies indicate that BAFF-BAFF-R signalling in activated B cells is dispensable for initial differentiation and formation of GC responses. However, it is absolutely required to sustain ongoing GC reactions. Intriguingly, despite suboptimal maintenance of the GC reactions, the impairment of BAFF-R signalling does not appear to affect the affinity-maturation and class-switching abilities of the responding B cells. We are currently investigating how BAFF-BAFF-R signalling in the GC impacts upon the selection of high affinity B cells necessary for mounting an effective antibody response against pathogens.