Immune cells are cells that play an important role in the immune response and immune protection of the human body. In general, immune cells include T lymphocytes, B lymphocytes, NK cells and other types, which have different structures and perform different functions, and by measuring the function of immune cells, a clear judgment of the immunity of the human body can be made. It is common to measure T lymphocyte subpopulation, that is, to test the function of T lymphocytes in the human body, because T lymphocytes include different types of CD3, CD4, CD8, etc. Through the measurement, we can understand whether the ratio of the number of T lymphocytes is within the normal range, and if these ratios are abnormal, it often means that the human body’s immune function is abnormal. By measuring the function of B lymphocytes, we can also understand whether the body is producing various immunoglobulins normally and make a general judgment of the body’s immune function. The measurement of NK cell function can also help to understand whether the body’s natural killer cells are functioning within normal limits.