The Chédiak-Higashi syndrome; the nature of the giant neutrophil granules and their interactions with cytoplasm and foreign particulates. I. Progressive enlargement of the massive inclusions in mature neutrophils. II. Manifestations of cytoplasmic injury and sequestration. III. Interactions between giant organelles and foreign particulates.

Defective bactericidal functioning of polymorphonuclear leukocytes (PMNs) from patients with the Chediak-Higashi syndrome (CHS) has been related in previous reports to a failure of the giant granules characteristics of the disorder to participate in degranulation after uptake of foreign particulates by neutrophils. However, the reason massive CHS inclusions do not fuse with and discharge their contents into phagocytic vacuoles has not been defined. The problem is particularly puzzling because it has been postulated that the hugh organelles in CHS neutophils originate by fusion of small azurophilic granules in promyelocytes and myelocytes. The present series of investigations into the cytopathology of the CHS has employed electron microscopy and ultrastructural cytochemistry to characterize the progressive enlargement of the hugh bodies in mature PMNs, their interaction with cytoplasmic constituents resulting in various manifestations of cell injury, and their response to foreign particulates. Each study clarifies abnormal features of the giant organelles essential to the understanding of their role in the defective bactericidal function of CHS neutrophils. The first report demonstrates that most of the hugh inclusions in PMNs are not primary lysosomes. The interaction and fusion of giant azurophilic granules with each other, with normal-sized primary and secondary granules, and with cytoplasmic components converts the massive primary granules into huge secondary lysosomes. Transformation to secondary hysosomes represents a critical alteration in the state of the giant granules that underlies their damaging influence on the cytoplasm and loss of reactivity wtih phagocytic vacuoles.