Both T cells and B cells are the immune cells of the body, which are differentiated from hematopoietic stem cells and work together to guard human health. First, T cells develop in the thymus, while B cells develop in the central immune organ, i.e., the bone marrow; second, they have different mechanisms of action: T cells mainly mediate cellular immunity, while B cells function only in humoral immunity. For example, when pathogens enter the blood and lymphatic fluid of the body, B cells are stimulated by external antigens and undergo morphological changes, increasing in size and forming plasma cells, which can secrete antibodies and remove antigens and play a humoral immune function; while when pathogens enter the cells, T cells can play a cytotoxic role and remove antigens or foreign substances to maintain health.