An Indo-US team of researchers has found that Indians, compared to other world populations, carry more of a kind of natural killer cells that can detect and terminate infections at an early stage1. Research suggests that Indians acquired the activating KIR (killer cell immunoglobulin-like receptors) genes as a result of natural selection to survive the environmental challenges during their pre-historic coastal migrations from Africa.

"Whether having more activating KIR genes is an advantage or disadvantage for Indians remains to be elucidated," says Rajalingam Raja, one of the reseachers.

White blood cells, or leukocytes, are cells of the immune system defending the body against disease by identifying and killing pathogens and tumor cells. The main types of WBC are T lymphocytes, B lymphocytes, macrophages, neutrophils and natural killer cells. The defense in the first week of infection is mediated primarily by macrophages, neutrophils and natural killer cells. In most cases, these cells do a great job of keeping people healthy and preventing infections. If the infection is not contained by the first week, the T and B lymphocytes will initiate more specific and strong defense.

Genes that control the immune response are generally variable among individuals, and such difference has been implicated in human health and disease.

Macrophages, neutrophils and natural killer cells have long been regarded as primitive and nonspecific. However, recent research revealed an unexpected complexity and sophisticated capability of these cells in detecting and terminating infections at the early stage. Particularly, the natural killer cells use a family of 14 killer cell immunoglobulin-like receptors (KIR) in detecting infections and tumors – 7 of them vary greatly between individuals and involve in activating natural killer cells. These activating KIR genes have been implicated in resistance to infections and susceptibility to autoimmune diseases.

The authors of this work are from: Department of Pathology and Laboratory Medicine, UCLA Immunogenetics Center, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA, USA; Department of Medicine, All India Institute of Medical Sciences, New Delhi, India; National Marrow Donor Program (NMDP), Minneapolis, MN, USA.