Interleukin-4 Induces a Switch of Human Intestinal Mast Cells from Proinflammatory Cells to Th2-Type Cells

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Abstract
Background: During the last years, mast cells have been recognized as a potent cellular source of multiple cytokines. However, little is known about the regulation of cytokine production by mature human mast cells derived from mucosal sites. Methods: Human mast cells were isolated from intestinal mucosa and cultured for 14 days in the presence of stem cell factor (SCF) alone or in combination with IL-4. Mast cells were then stimulated by IgE receptor cross-linking or bacterial infection and cytokine production was examined by RT-PCR and ELISA. Results: We found that human intestinal mast cells produce proinflammatory cytokines such as TNF-α, IL-1β and IL-6 without further stimulation. Stimulation of the cells with gram-negative bacteria (Escherichia coli and others) caused an upregulation of TNF-α expression. Following IgE receptor cross-linking, we found additional expression of the Th2 cytokines IL-3, IL-5 and IL-13. Interestingly, mRNA for IL-3, IL-5 and IL-13 was also expressed in unstimulated mast cells provided they were cultured in the presence of SCF and IL-4. Moreover, IL-4 rendered mast cells capable of releasing IL-5 in response to bacterial challenge. Conclusion: In the presence of the mast cell survival factor SCF, mature human mast cells produce predominantly proinflammatory cytokines, whereas in the presence of SCF and IL-4, mast cells produce not only proinflammatory but also Th2 cytokines.