FCGR2B and nephritis: IL-1β is a potent proinflammatory cytokine that has previously been identified in glomerular macrophages in diseased MRL-lpr mice (39) as well as Fcgr2b−/− mice (41), while elevated renal IL-1 family cytokine responses are common to several models of nephritis (SI Appendix, Fig. S6A).