Innate myeloid cells under the control of adaptive immunity: the example of mast cells and basophils

• As other myeloid cells, mast cells and basophils are effectors of innate immunity.
• Mast cell and basophil activities are controlled by antibodies via FcRs.
• Antibodies enroll mast cells and basophils in adaptive immunity.
• Antibodies modulate, positively and negatively, mast cell and basophil activation.
• Antibodies modulate qualitatively mast cell secretory responses.

Mast cells and basophils are mostly known as the initiators of IgE-dependent allergic reactions. They, however, contribute to innate immunity against pathogens and venoms. Like other myeloid cells, they also express receptors for the Fc portion of IgG antibodies. These include activating receptors and inhibitory receptors. Because IgG antibodies are produced in exceedingly higher amounts than IgE antibodies, IgG receptors are co-engaged with IgE receptors under physiological conditions. Mast cells and basophils are examples of the many innate myeloid cells whose effector functions are used and finely tuned by antibodies. They can be thus enrolled in a variety of adaptive immune responses, their activation can be regulated, positively and negatively and their biological responses can be modulated qualitatively by antibodies.