IgE-mediated mast cell degranulation and recovery monitored by time-lapse photography

Background: Mast cells are long-lived resident cells that are of great impo rtance in an allergic reaction. It has previously been suggested that after IgE-mediated degranulation mast cells can undergo regranulation. Such a pr ocess is probably of great importance with respect to the severity and perp etuation of the allergic response. Objective: Our purpose was to investigate whether mast cells recover from d egranulation 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 ant igen with a 24-hour or 48-hour interval. During each of the 2 activation st ages, release of beta -hexosaminidase was measured by means of enzymatic co lorimetric analysis, and IL-13 and IL-6 mRNA was detected by ribonuclease p rotection assay. Both scanning electron microscopy and time-lapse photograp hy 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 t o what is seen in the initial activation. Scanning electron microscopy docu mented cells at various stages during the recovery process 30 minutes after the activation. With time-lapse photography, a single cell that had underg one degranulation could be visualized consecutively during its recovery pro cess. Conclusion: Mast cells can recover after an IgE-mediated activation and can repeatedly release beta -hexosaminidase and express IL-6 and IL-13 mRNA af ter re-activation.