BACKGROUND: Mast cells are long-lived resident cells that are of great 
importance in an allergic reaction. It has previously been suggested that after 
IgE-mediated degranulation mast cells can undergo regranulation. Such a process 
is probably of great importance with respect to the severity and perpetuation of 
the allergic response.
OBJECTIVE: Our purpose was to investigate whether mast cells recover from 
degranulation and whether they still have the potential to release a 
granule-associated mediator and upregulate certain cytokine genes.
METHODS: Mouse mast cells were repeatedly activated by IgE and specific antigen 
with a 24-hour or 48-hour interval. During each of the 2 activation stages, 
release of beta-hexosaminidase was measured by means of enzymatic colorimetric 
analysis, and IL-13 and IL-6 mRNA was detected by ribonuclease protection assay. 
Both scanning electron microscopy and time-lapse photography were used to reveal 
the process of mast cell recovery.
RESULTS: We found that re-activation of degranulated mast cells in response to 
high-affinity IgE-receptor cross-linkage triggers beta-hexosaminidase release 
and upregulation of IL-13 and IL-6 gene expression levels similar to what is 
seen in the initial activation. Scanning electron microscopy documented cells at 
various stages during the recovery process 30 minutes after the activation. With 
time-lapse photography, a single cell that had undergone degranulation could be 
visualized consecutively during its recovery process.
CONCLUSION: Mast cells can recover after an IgE-mediated activation and can 
repeatedly release beta-hexosaminidase and express IL-6 and IL-13 mRNA after 
re-activation.