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Unformatted text preview: sis. (B, courtesy of D. R.
Green/La Jolla Institute for Allergy and
Immunology; C, courtesy of Ken Adams,
Boston University.) This material cannot be copied, reproduced, manufactured, or disseminated in any
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© 2009 Sinauer Associates, Inc. UNCORRECTED PAGE PROOFS
CELL DEATH AND CELL RENEWAL Normal cell Cytosol Outside
of cell –
– – Phosphatidylserine FIGURE 17.2 Phagocytosis of
apoptotic cells Apoptotic cells and
cell fragments are recognized and engulfed by phagocytic cells. One of the
signals recognized by phagocytes is
phosphatidylserine on the cell surface.
In normal cells, phosphatidylserine is
restricted to the inner leaflet of the
plasma membrane, but it becomes
expressed on the cell surface during
apoptosis. Apoptosis Receptor –
– – Phagocytic cell usually fragmented as a result of cleavage between nucleosomes. The chromatin condenses and the nucleus then breaks up into small pieces. Finally,
the cell itself shrinks and breaks up into membrane-enclosed fragments
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