A comparison of the gene density across the KIR, LILR, and MHC-DRB regions of humans and rhesus macaques. The gene density (genes/Mb) is plotted for the KIR, LILR, and MHC-DRB regions in humans (red) and rhesus macaques (blue). The level of significance between the 2 species is indicated with asterisks (*P < 0.05, ****P < 0.00005). The overall gene densities of the rhesus macaque and human reference genomes are indicated with dashed lines.