In vivo APRIL antagonism reduces PC numbers in BM. (A) Mice were primed/boosted with OVA and treated for 6 weeks with Apry-1-1 or cIg. The figure shows the number of PCs secreting anti-OVA Igs recovered from BM after treatment. (B) Splenocytes from OVA-primed/boosted mice were transferred into recipient mice treated previously with Apry-1-1 or cIg. The figure shows the number of BM PCs secreting anti-OVA Igs 2 days after transfer.