Immunity is a modern medical term, that is, the ability of human body to resist diseases. In traditional Chinese medicine, immunity means healthy qi. If you are healthy, you are not easy to get sick; Lack of healthy qi can lead to one disease or another. Therefore, TCM health preservation is actually to maintain healthy qi, that is, the qi of the five internal organs. The most important ones are kidney qi, spleen qi and lung qi. The influence of the three factors on immunity is that kidney deficiency is greater than spleen deficiency, and spleen deficiency is greater than lung deficiency. Although the three have different effects on immunity, no matter which system is weak, it will lead to low immunity. Therefore, in Chinese medicine, there are three aspects to improve healthy qi: tonifying kidney, strengthening spleen and tonifying lung. First of all, the kidney stores essence, promotes human growth, development and reproduction, and preserves the metabolism of water and body fluids, so it is also called "water dirty". At the same time, the kidney governs qi, which is the "root of qi". The ancients said that "life gate always depends on two kidneys, and both kidneys belong to life gate", emphasizing that kidney is the root of yin and yang of five internal organs. Therefore, to tonify vital qi, we must first tonify kidney qi. Secondly, the spleen governs transport and transformation, which can turn food into subtle and spread it to the whole body. At the same time, spleen governs blood, which not only captures blood, but also transforms Shui Gu into blood imperceptibly, thus nourishing the whole body. Thirdly, the lung governs qi, and the respiratory function of the lung is normal, so that the whole body qi can be controlled. Through breathing, the natural clear gas is sucked into the chest, which is combined with the essence of Shui Gu transported by the spleen to produce the ancestral gas. The vitality is opposite to the ancestral spirit, which is the foundation of the human body, but it is weak. Only when the ascending ancestor spirit is in the chest, the two kinds of qi are connected, and then the essence of Shui Gu and the natural qi are obtained, can it thrive and nourish the whole body.