Membrane unpacking and the rapid disposal of apoptotic cells

There is evidence that macrophages can recognize phosphatidylserine (PS) on the surface of apoptotic thymocytes, where PS exposure relates to looser packing (‘unpacking’) of the polar headgroups of the outer lamina, detectable by lipophilic dyes (Fadok, V.A., Voelker, D.R., Campbell, P.A., Cohen, J....

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Bibliographic Details
Published in:Immunology letters 1995-12, Vol.48 (3), p.159-166
Main Authors: Ashman, Robert F., Peckham, David, Alhasan, Samir, Stunz, Laura L.
Format: Article
Language:English
Subjects:
Animals
Apoptosis - immunology
Apoptotic cell
Cell Membrane - immunology
Cells, Cultured
DNA cleavage
DNA Damage
Female
Male
Mice
Mice, Inbred C57BL
Mice, Inbred DBA
Reproducibility of Results
Spleen - cytology
T cell
T-Lymphocytes - cytology
T-Lymphocytes - immunology
Thymocyte
Thymus Gland - cytology
Thymus Gland - immunology
Time Factors
Unpacking
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Summary:There is evidence that macrophages can recognize phosphatidylserine (PS) on the surface of apoptotic thymocytes, where PS exposure relates to looser packing (‘unpacking’) of the polar headgroups of the outer lamina, detectable by lipophilic dyes (Fadok, V.A., Voelker, D.R., Campbell, P.A., Cohen, J.J., Bratton, D.L., and Henson, P.M. (1992) J. Immunol. 148, 2207). We have shown that membrane unpacking also occurs in B cells, where this event actually precedes DNA cleavage (Mower, D.A. Jr., Peckham, D.W., Illera, V.A., Fishbaugh, J.K., Stunz, L.L. and Ashman, R.F. (1994) J. Immunol. 152, 4832). This paper demonstrates that the time interval between membrane unpacking (detected as merocyanine 540 binding) and DNA cleavage (detected by flow cytometry of propidium iodide stained nuclei) also occurs in both T cells and thymocytes. The tight coupling of these two apparently distinct events is emphasized by their co-regulation by a variety of agents which accelerate or inhibit apoptosis. One hypothesis to explain the very low numbers of free apoptotic cells seen in vivo is that macrophages can recognize cells with unpacked membranes and destroy them before they cleave their DNA. In support of this hypothesis, we demonstrated that parenteral cycloheximide triggers a wave of apoptosis in the spleen detected by merocyanine 540 as well as by hypodiploid nuclei. Significantly, both parameters returned from peak values at 2 h virtually to normal by 4 h, testifying to the existence of a rapid disposal mechanism in vivo for cells with unpacked membranes as well as hypodiploid nuclei.
ISSN:0165-2478
1879-0542
DOI:10.1016/0165-2478(95)02471-9