Contributions of IL-1β and IL-1α to crescentic glomerulonephritis in mice

Interleukin-1 (IL-1) is a pleiotropic proinflammatory cytokine with two distinct isoforms (IL-1alpha and IL-1beta) that signal through the same IL-1 type I receptor (IL-1RI). Contributions of IL-1beta have been demonstrated in human and experimental proliferative glomerulonephritis (GN), but the involvement of IL-1alpha has received little attention. To determine the combined contribution of IL-1alpha and IL- 1beta and to dissect the specific contribution of IL- 1beta, the development of antiglomerular basement membrane globulin-induced crescentic GN was studied in mice genetically deficient in either the IL- I receptor type I (IL-1RI-/-), which are unresponsive to both IL-1alpha and IL-1beta, or IL-1beta alone IL-1beta-/- mice showed significant reductions in crescent formation and glomerular T cell and macrophage recruitment compared with strain matched controls (WT). No additional reductions of these indices of injury were observed in IL-1RI-/- mice. However, IL-1RI-/- mice showed greater functional renal protection with significantly less proteinuria and reduced serum creatinine compared with IL-1beta-/- mice, suggesting a significant contribution of IL-1alpha to these parameters of injury. IL-1RI-/- mice had lower serum titers of antibody to the nephritogenic antigen (sheep globulin) and reduced glomerular deposition of complement compared with either IL-1beta-/- or WT mice. This suggests that in the absence of responses to both IL-1alpha and IL-1beta, attenuation of humoral mediators provides additional functional protection from renal injury that is not seen in the absence of IL-1beta alone. These studies indicate that IL-1beta but not IL-1alpha contributes to crescent formation and inflammatory cell recruitment, whereas IL-1alpha but not IL-1beta contributes to humoral mechanisms of glomerular injury.