(A) In the absence of cytokine, the IL-1 receptor chains IL-1R1 and IL-1RAcP remain dissociated and fail to signal.
(B) IL-1 (either IL-1alpha or IL-1beta) brings IL-1R1 and IL-1RAcP together to enable signal initiation.
(C) Anakinra is a recombinant human IL-1 receptor antagonist that binds IL-1R1 but not IL-1RAcP, preventing IL-1 from bringing these receptor chains together.
(D) Canakinumab is an IgG1 antibody that binds IL-1beta, preventing interaction with the IL-1 receptor.
(E) Rilonacept is a fusion protein consisting of fused extracellular domains of IL-1R1 and IL-1RAcP attached to each arm of an IgG1 Fc portion, forming an "IL-1 trap" that binds IL-1alpha, IL-1beta, and (to a lesser extent) IL-1ra.
