Ultrastructural criteria for identification of mast cells and basophils in humans, guinea pigs, and mice.

Basophils and mast cells represent distinct populations that may express differences in function, biochemistry, and response to drugs. In this review, we define ultrastructural criteria useful in distinguishing basophils from mast cells in humans, the guinea pig, and the mouse. Although the ultrastructural features of normal mature basophils and mast cells are the main subject of this report, we also describe variations in basophil and mast cell ultrastructure that reflect the cells' functional activity or stage of maturation. Appreciation of such ultrastructural changes, which can strikingly alter the appearance of these cells, is particularly important in identifying basophils and mast cells in sites of inflammation. In addition to facilitating the accurate identification of basophils and mast cells in vivo, ultrastructural analysis has played an important role in in vitro studies of basophil and mast cell maturation and function. The morphology and biochemistry of these cells now can be studied either by analyzing highly purified populations derived from blood or tissues, notably the lung, or by examining cloned cell lines maintained in vitro. Exploitation of these important technical advances promises to rapidly increase our understanding of the roles of basophils and mast cells in health and disease.