ABSTRACT
Killer cell immunoglobulin-like receptors (KIR) are the key receptors of human natural killer (NK) cells that mount an early immune response against infection and tumors. The number and type of KIR genes are substantially variable between individuals and populations. Recently we reported KIR gene content diversity in a Persian population living in the southern province of Fars, which is comparable to that of European Caucasians. These results are consistent with the ethnic ancestry and affinity between Persians and Caucasians. Herein we analyzed another Persian population living in the northern province of Tehran and discovered an unexpected increase in the distribution of KIR2DS5 and its linked loci KIR3DS1, -2DS1, and -2DL5 in northern Persians compared with that reported in the southern Persian population. Although the geographic barriers may have limited the gene flow, the impact of the local environment on the natural selection of KIR2DS5 and its linked loci in the northern Persians cannot be completely ruled out. The difference in northern and southern populations in activating KIR gene content creates an appealing hypothesis that KIR2DS5-enriched northern Persians are more resistant to developing clinical conditions demonstrated to be associated with KIR2DS5, such as psoriasis vulgaris, endometriosis, ankylosing spondylitis, and acute rejection of kidney grafts, compared with those living in the southern part of the country.