The development of type II collagen-induced arthritis (CIA) in DBA/1 mice is readily accelerated by treatments with interleukin-1 beta (IL-1 beta). In an attempt to further characterize this IL-1 beta-mediated enhancement of CIA, we first examined the effects of IL-1 beta treatments in other "CIA-susceptible" strains and "CIA-resistant" mice. It was observed that treatments with IL-1 beta also enhanced the onset of arthritis in two B10 recombinant CIA-susceptible strains, B10.T (6R) and B10.DA, and in the SJL mice which develop CIA with a relatively low and variable incidence. On the other hand, IL-1 beta failed to augment the expression of arthritic disease in several CIA-resistant strains. We also investigated the potentiating effects of IL-1 beta in mice that were depleted of L3T4+ T cells. It was found that the ability of IL-1 beta to accelerate the development of CIA was significantly reduced in DBA/1 mice pretreated with the monoclonal anti-L3T4 antibody. In further studies, we demonstrated that the induction of CIA upon transfer with collagen-primed spleen cells was also augmented by IL-1 beta, and this enhancing effect by IL-1 beta on the adoptive transfer of CIA was associated with a significant increase in the levels of serum anti-collagen antibodies. Moreover, IL-1 beta treatments did not potentiate the induction of CIA in mice that were transferred with either collagen-immune splenic cells that were depleted of L3T4+ T cells or only T cells obtained from collagen-immunized animals. However, IL-1 beta enhanced the development of arthritis in animals that had been transferred with two subpopulations of collagen-immune cells: (i) enriched T cells and (ii) splenic cells that were depleted of L3T4+ T cells. Thus, IL-1 beta potentiated the inflammatory responses in animals that were genetically predisposed to developing arthritis. In contrast, IL-1 beta was incapable of accelerating the development of arthritis in various mouse strains that were genetically resistant to CIA. The administration of IL-1 beta also failed to potentiate the development of CIA in L3T4-deficient mice or in animals transferred with collagen-primed spleen cells that were depleted of L3T4+ T cells. These results indicate that IL-1 beta readily accelerates the induction of arthritis when the disease is present, but that IL-1 beta is incapable of promoting the expression of the arthritis in the absence of underlying disease.