Interleukin-1β measured by radioimmunoassay in the rat spleen and thymus is increased during chronic inflammatory stress

We have developed an extraction method and radioimmunoassay for the measurement of interleukin-1β (IL-1β) in rat tissues, using an antibody specific for IL-1β. IL-1β was detected in the spleen and thymus of control rats. Adrenalectomy (ADX) had no effect upon control levels of IL-1β. In animals with adjuvant-induced arthritis, IL-1β content in the spleen and thymus increased after 14 days. These increases in tissue IL-1β contents were not evident in ADX arthritic animals. We conclude that IL-1β synthesis is stimulated in tissues of the immune system following the development of adjuvant-induced arthritis. Failure to observe elevated levels of tissue IL-1β in ADX arthritic rats may be evidence for tissue depletion due to increased IL-1β release in the absence of circulating corticosteroids.