CD40-CD40L interaction is responsible for the induction of IL-1β synthesis by DCs.

(A) DCs were incubated for different periods as indicated with CD40L transfected cells at a CD40L⁺ cell:DC ratio of 1:1. At the end of each incubation time, the intracellular content in pro–IL-1β was analyzed by Western blot and quantified by densitometry. (B) DCs were incubated for 8 hours alone (lane 1) or with alloreactive T cells (lanes 2 and 3), that were untreated (lane 2) or pretreated for 30 minutes with anti CD40L antibody, at T-cell:DC ratio 10:1. At the end of incubation the intracellular content in pro–IL-1β was analyzed by Western blot.