In the absence of a CD40 signal, B cells are tolerogenic.
Buhlmann JE, Foy TM, Aruffo A, Crassi KM, Ledbetter JA, Green WR, Xu JC, Shultz LD, Roopesian D, Flavell RA, et al. In the absence of a CD40 signal, B cells are tolerogenic. Immunity. 1995 Jun; 2(6):645-53.