“Natural Killer cells” maintain full readiness to kill uninvited guests in HIV infected chimpanzees

Natural Killer (NK) cells are the foot-soldiers of the immune system. It is their task to eliminate invaders (such as virusses) as quickly as possible. In humans different types of NK cells protect in different ways, either directly, for example by making holes in unwanted cells to insert poisonous substances or indirectly, by secreting cytokines that signal other cell types that there is a problem.

Why do we then get ill despite these “heavily armed defenders in full readiness”? Unfortunately for humans and animals, invaders such as virusses, parasites and bacteria have developed their own strategies to overcome this defence system. By studying these strategies we can develop therapies that eventually will conquer the invaders.

In contrast to humans, chimpanzees do not get seriously ill from HIV. In infected humans, NK cells are rapidly disabled by the HIV; what is left is a population of exhausted, weakened NK cells. What happens in chimpanzees? Although BPRC has long stopped research in chimpanzees, it is ethically important to obtain as much information as possible from previous research. By using cells frozen during earlier studies, the role of NK cells in HIV infected chimpanzees was investigated (article Pubmed). The results indicate that chimpanzees NK cells are less specialized than human NK cells: one type of chimpanzee NK cell kills both in direct and indirect ways. Interestingly, and in contrast to humans, NK cells from HIV infected chimpanzees maintained full readiness and capacity to kill invaders.