Basophil. Artwork of basophil white blood cells. Basophils are the smallest and least common of the white blood cells. The cell at right has been sectioned to show its internal structure. The nucleus, which stores the cell's genetic information, is purple. Golgi apparatus (orange) processes proteins that are to be secreted from the cell into vesicles. Basophils are cells of the body's immune system involved in allergic and inflammatory reactions. They secrete the chemicals heparin, histamine and serotonin, which are stored in granules (green and yellow) in the cell's cytoplasm.