Natural killer (NK) cell deficiency is a genetic disorder that is passed down from parents to their children. Currently, five different genes have been shown to cause NK cell deficiency. Each of these genes is passed down as an autosomal recessive trait. In other words, the patient must inherit one mutated gene from each parent in order to develop the disorder. Individuals who only have one mutated gene and do not experience symptoms are called carriers.
Carriers have a 50% chance of passing the abnormal gene to each of their children. If both parents are carriers of the gene, there is a 25% chance that each of their children will inherit the disease and a 50% chance that each of their children will be a carrier.
Patients with natural killer (NK) cell deficiency suffer from frequent infections, especially lung infections and herpes virus infections.
There is also evidence suggesting that patients with NK cell deficiency have an increased risk of developing cancer. This is because NK cells are the body's first line of defense against cancerous growths in the body. Some studies also suggest that cancer patients with NK cell deficiency may not respond as well to treatments as patients who do not have the disorder.
DNA analysis: A DNA analysis is the most conclusive diagnostic test for natural killer (NK) cell deficiency. During the procedure, a small sample of the patient's blood is sent to a laboratory that performs genetic testing. The sample is then analyzed for the presence of genes that are associated with the disorder. This test may be performed if NK cell deficiency is suspected or if it is suspected that the patient may be a carrier.
Natural killer cell count: If NK cell deficiency is suspected, a natural killer cell count may be conducted. During the procedure, a small sample of blood is taken from the patient, and the number of NK cells is measured. In healthy individuals, NK cells make up about 15% of the mononuclear cells (cells with one nucleus) in the blood. These levels typically fluctuate to some degree. For instance, patients experience a rapid increase in NK cells in response to an infection, followed by a decrease for five to seven days after the infection. Patients who have low or absent levels of NK cells and are not recovering from a recent infection receive a positive diagnosis.
Natural killer cell function assay: An NK cell function assay can determine whether a patient has deficient levels of NK cells in the blood. A sample of blood is taken from the patient. A special machine removes the NK cells from the sample. These cells are then placed on a petri dish along with cells (such as viruses) that should trigger them to kill. If the patient has normal levels of healthy NK cells, the NK cells will kill the other cells on the petri dish. After a few hours, a colored dye is added to the petri dish. This dye will only saturate the dead cells. Then, a device called a flow cytometer will then measure how many cells the NK cells killed. If the NK cells do not kill enough of the cells, a positive diagnosis can be made.
Prenatal DNA analysis: Pregnant mothers may have their unborn children tested for NK cell deficiency. In order to retrieve a sample of the fetus' cells for testing, amniocentesis or chorionic villus sampling may be performed. During amniocentesis, a long, thin needle is inserted into the pregnant woman's abdominal wall and into the uterus. A small amount of fluid is removed from the sac surrounding the fetus. During chorionic villus sampling (CVS), a small piece of tissue, called chorionic villi, is removed from the placenta. There are risks associated with these both of these procedures, including miscarriage. Patients should discuss the potential risks and benefits of these procedures with their healthcare providers.