Numbers decrease after periods of stress. Eosinophils are about the same size as neutrophils, but have reddish-orange granules. Basophils are elevated due to allergens, Hodgkin's disease, smallpox, after splenectomy, chronic hemolytic anemia and some cancers. They are elevated, also, during recovering lobar pneumonia, acute rheumatic fever and anaphylactoid purpura. They are decreased in the acute phases of the same conditions.
Basophils are the precursors for mast cells.
Mast cells are in tissues and, when adequately stimulated by allergens, cause the release of histamine, heparin and serotonin. More detail may be obtained by reviewing the lectures on immunity in BIOL 251. Basophils are the same size as eosinophils, but have purplish to blue-black granules. Agranular WBC also come from red bone marrow, but require further maturation in lymphoid tissue. They have NO granules.