Illustration depicting<unk>  activation and anaphylaxis<unk> <unk> s are very similar to basophil granulocytes (a class of white blood cells) in blood. Both are granulated cells that contain histamine and heparin, an anticoagulant. Their nuclei differ in that the basophil nucleus is lobated while the<unk>  nucleus is round. The Fc region of immunoglobulin E (IgE) becomes bound to<unk> s and basophils and when IgE's paratopes bind to an antigen, it causes the cells to release histamine and other inflammatory mediators. These similarities have led many to speculate that<unk> s are basophils that have "homed in" on tissues. Furthermore, they share a common precursor in bone marrow expressing the CD34 molecule. Basophils leave the bone marrow already mature, whereas the<unk>  circulates in an immature form, only maturing once in a tissue site. The site an immature<unk>  settles in probably determines its precise characteristics. The first in vitro differentiation and growth of a pure population of mouse<unk> s has been carried out using conditioned medium derived from concanavalin A-stimulated splenocytes. Later, it was discovered that T cell-derived interleukin 3 was the component present in the conditioned media that was required for<unk>  differentiation and growth.<unk> s in rodents are classically divided into two subtypes: connective tissue-type<unk> s and mucosal<unk> s. The activities of the latter are dependent on T-cells.<unk> s are present in most tissues characteristically surrounding blood vessels, nerves and lymphatic vessels, and are especially prominent near the boundaries between the outside world and the internal milieu, such as the skin, mucosa of the lungs, and digestive tract, as well as the mouth, conjunctiva, and nose.
Mast cell
T cell
Reactive lymphocyte
Dendritic cell
Natural killer cell
Prolymphocyte
Nonspecific immune cell
Basophil