The origin, content, and fate of azurophil granules of blood monocytes were investigated in several species (rabbit, guinea pig, human) by electron microscopy and cytochemistry. The life cycle of monocytes consists of maturation in bone marrow, transit in blood, and migration into tissues where they function as macrophages. Cells were examined from all three phases. It was found that: azurophil granules originate in the Golgi complex of the developing monocyte of bone marrow and blood, and ultimately fuse with phagosomes during phagocytosis upon arrival of monocytes in the tissues. They contain lysosomal enzymes in all species studied and peroxidase in the guinea pig and human. These enzymes are produced by the same pathway as other secretory products (i.e., they are segregated in the rough ER and packaged into granules in the Golgi complex). The findings demonstrate that the azurophil granules of monocytes are primary lysosomes or storage granules comparable to the azurophils of polymorphonuclear leukocytes and the specific granules of eosinophils. Macrophages from peritoneal exudates (72–96 hr after endotoxin injection) contain large quantities of lysosomal enzymes throughout the secretory apparatus (rough ER and Golgi complex), in digestive vacuoles, and in numerous coated vesicles; however, they lack forming or mature azurophil granules. Hence it appears that the monocyte produces two types of primary lysosomes during different phases of its life cycle—azurophil granules made by developing monocytes in bone marrow or blood, and coated vesicles made by macrophages in tissues and body cavities.
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1 August 1971
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August 01 1971
DIFFERENTIATION OF MONOCYTES : Origin, Nature, and Fate of Their Azurophil Granules
Barbara A. Nichols,
Barbara A. Nichols
From the Department of Pathology, University of California, San Francisco, California 94122.
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Dorothy Ford Bainton,
Dorothy Ford Bainton
From the Department of Pathology, University of California, San Francisco, California 94122.
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Marilyn G. Farquhar
Marilyn G. Farquhar
From the Department of Pathology, University of California, San Francisco, California 94122.
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Barbara A. Nichols
From the Department of Pathology, University of California, San Francisco, California 94122.
Dorothy Ford Bainton
From the Department of Pathology, University of California, San Francisco, California 94122.
Marilyn G. Farquhar
From the Department of Pathology, University of California, San Francisco, California 94122.
Dr. Farquhar's present address is The Rockefeller University, New York 10021
Received:
October 30 1970
Revision Received:
January 13 1971
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1971 by The Rockefeller University Press
1971
J Cell Biol (1971) 50 (2): 498–515.
Article history
Received:
October 30 1970
Revision Received:
January 13 1971
Citation
Barbara A. Nichols, Dorothy Ford Bainton, Marilyn G. Farquhar; DIFFERENTIATION OF MONOCYTES : Origin, Nature, and Fate of Their Azurophil Granules . J Cell Biol 1 August 1971; 50 (2): 498–515. doi: https://doi.org/10.1083/jcb.50.2.498
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