A recent meta-analysis has demonstrated an association between a molecular weight variant of CR1 and SLE.11 Further, in the mouse, CR1/CR2 (encoded by alternatively spliced forms of the same gene) is a lupus susceptibility gene12, 13 important in the modulation of the antinuclear autoantibody response.14, 15. This evidence concerns the gene CR1 and systemic lupus erythematosus.