Macrophage is one of immune cells that phagocytose and eliminate foreign bodies and bacteria invaded in a human body. There is also neutrophil in immune cells that phagocytose in the same way. But macrophage has longer life and its phagocytic ability is said to be several times more powerful than neutrophil's. Moreover, macrophage has antigen-presenting function, which makes a great difference between them.

A neutrophil is phagocytizing bacteria. Neutrophils are the majority of white blood cell and they have occupied up to 70%. They play important roles in biological defense by phagocytizing and eliminating bacteria that invaded a living body, and this biological mechanism is called innate immune system. Phagocytosed bacteria are taken into the phagosome and sterilized by reactive oxygen species (ROS), emitting green fluorescence.

Mast cells are releasing granules that have been stored in their cytoplasms, this phenomenon called the degranulation. They exist in mucosal and connective tissues throughout the whole body. Around the cell membrane of the mast cells, lots of IgE antibodies have adhered and they recognize foreign substances entering from the outside of the body. It is by antigens attaching to these IgE antibodies that the degranulation is triggered. These granules contain chemical mediators such as histamine and they consequently cause immediate allergic reactions—for example, hay fever and urticaria.