NEMO submerged in virus-prone boys

Natural killer (NK) cells provide an important line of host defense, acting both with and without help from the clonal immune system to destroy virally infected and malignantly transformed host cells. NK cell biologists distinguish between two modes of cell killing, one dependent on a humoral response to the target cells (antibody dependent cellular cytotoxicity; ADCC) and the other antibody-independent (NK cell cytotoxicity). To date, they have been unable to tease apart the contributions of these mechanisms to human health, but Orange et al. now report on a mutation of the adaptor protein NEMO that impairs the latter while sparing the former. NEMO is the product of an essential X-linked gene, and it mediates many of the effects of the ubiquitous NFkB pathway. Nevertheless, certain mild mutations in NEMO are compatible with development in males. Boys carrying one of these mutations show various developmental and dermatological abnormalities, as well as recurrent bacterial and viral infections, but they can survive well into adolescence. Orange et al. focus here on the unusual properties of the NK cells from 3 such patients, each of whom carries a distinct NEMO missense mutation. NK cells from these boys fail to kill a tumor cell line that is normally targeted by NK cell cytotoxicity, but they are active (even unusually so) in ADCC assays . Orange et al. find that IL-2 supplementation can rescue NK cell cytotoxicity, suggesting a parallel route to cell killing that might be of use in treating these patients or even to enhance NK activity in other settings.

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