Increased frequencies of activating KIR genes and of inhibitory KIR genes, which encode receptors with lower affinities for their MHC class I ligands, have been associated with several human autoimmune and chronic inflammatory conditions that include sepsis, ankylosing spondylitis, systemic lupus erythematous, leukemia, type 1 diabetes, and autism [49–54], reviewed in [15, 16]. The gene discussed is KIR3DL1; the disease is type 1 diabetes mellitus.