CD1D and systemic lupus erythematosus: Although this study used N10-N14 backcrossed mice that are expected to carry ≤0.1% genes from the 129/B6 β2m° or CD1d° founders, there remains the possibility that our results reflect the alteration of linked gene(s) during the backcross of the mutated β2m or CD1d 129 locus onto the lupus genetic backgrounds.