The cover features a digitally-coloured histology image of a renal glomerulus from an IgG Fc receptor IIB (FcγRIIB)-deficient C57BL/6 (KO1) mouse. The original periodic acid-Schiff/hematoxylin-stained section showed that KO1 mice have normal glomerular histology despite the development of rheumatoid arthritis (RA). The image is taken from the article by Kawano et al. (pp. 770–778) in which it is shown that the introduction of a Y chromosomelinked autoimmune acceleration (Yaa) mutation in the KO1 strain (KO1.Yaa) leads to the development of systemic lupus erythematosus (SLE) rather than RA. Kawano et al. suggest that their model clarifies the shared and disease-specific mechanisms underlying the clinically distinct autoimmune diseases RA and SLE. The added colour is purely for aesthetic purposes and has no biological relevance.