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Clinical and Diagnostic Laboratory Immunology, May 1995, 297-301, Vol 2, No. 3
MS Kaminer, GF Murphy, B Zweiman and RM Lavker
Previous studies have identified two ultrastructurally distinct forms of
mast cell (MC) degranulation following activation. Immunoglobulin E
(IgE)-mediated reactions are characterized by a very rapid swelling and
fusion of MC granules and abrupt mediator release. In certain chronic
disease states (e.g., bullous pemphigoid), there is "piecemeal"
degranulation with a more-gradual mediator release effected by
microvesicular transport of "pieces" of granules to the cell surface. It is
unclear whether these two degranulation patterns are determined by the
different natures of the stimuli, heterogeneity among responding MC
granules, or temporal factors. To investigate these issues, we have carried
out electron microscopic studies with skin biopsies obtained from
ragweed-sensitive subjects 15 and 30 s and 1, 3, 5, and 10 min after
intradermal ragweed injection. "Anaphylactic"-type granule changes began by
15 s after ragweed injection and were complete by 5 min; unaffected
granules were juxtaposed with granules that were swollen and fused. The
remaining granules subsequently underwent changes in appearance similar to
those seen in piecemeal degranulation. However, microvesicular transport of
granule components to the surface was not observed. These findings indicate
that skin MC changes in sites of IgE-mediated reactions include not only
the typical very rapid anaphylactic degranulation but also a slower onset
of gradual alteration of other granules, frequently within the same MC.
These different patterns could reflect MC granule heterogeneity with
attendant different responses to IgE-mediated stimuli.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Connective tissue mast cells exhibit time-dependent degranulation heterogeneity
Department of Dermatology, University of Pennsylvania, Philadelphia, USA.
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