- APRIL-deficient mice have normal immune system development. Varfolomeev, E., Kischkel, F., Martin, F., Seshasayee, D., Wang, H., Lawrence, D., Olsson, C., Tom, L., Erickson, S., French, D., Schow, P., Grewal, I.S., Ashkenazi, A. Mol. Cell. Biol. (2004)