NK cells are natural killer cells, which are important immune cells of the body. low absolute number of NK cells may be due to physiological factors, or due to pathological factors, such as chronic hepatitis, immunodeficiency. 1. Physiological factors: lack of exercise, staying up late, etc., will reduce the body’s immunity, making the body susceptible to disease, which leads to low NK cells. In this case, you need to actively exercise, maintain sufficient sleep, avoid staying up late, so as to enhance the body’s resistance. 2. Pathologic factors. (1) Hepatitis: for those who suffer from hepatitis B, the hepatitis B virus will damage the liver, leading to weakened metabolic function of the body, which in turn will lead to decreased immunity and a continuous decline in NK cells, which in turn will lead to continuous infection by the hepatitis B virus, resulting in chronic hepatitis B. (2) Immunodeficiency: Immunodeficiency is a disease caused by a developmental defect in the body’s immune system, resulting in low resistance to infection. Because of the obvious defects in the immune system, the immune function is low, resulting in low NK cells. Abnormal examination indicators should be diagnosed and treated early. Have a good life habit on weekdays.