In experimental arthritis, glucocorticoid secretion is inadequate relative to inflammation. We hypothesized that IL-1 is a key factor for inadequate glucocorticoid secretion in arthritic rats. Collagen type II-induced arthritis (CIA) in DA rats was the model to study effects of IL-1 on adrenal function. In the CIA model, an increase of intraadrenal MHCII-positive cells was observed. MHCII-positive cells or bone marrow-derived dendritic cells inhibited glucocorticoid secretion of adrenal gland cells. IL-1, but also IL-18 and the inflammasome were critical in glucocorticoid inhibition. Arthritic compared to control adrenal gland cells produced higher amounts of CXC chemokines from MHCII+ adrenal cells, particularly CINC-2, which is strongly dependent on presence of IL-1. In CIA, macrophages and/or dendritic cells inhibit glucocorticoid secretion via IL-1 in adrenal glands. These findings show that activated macrophages and/or dendritic cells inhibit glucocorticoid secretion in experimental arthritis and that IL-1β is a decisive factor.