Mast cells are critical for the degranulation‐induced shift from Th1 to Th2 immune responses in vivo

Abstract

The involvement of mast cells on the generation of Th2 responses has been suggested; however, it is still unclear whether mast cells are critical for the degranulation‐induced shift from Th1 to Th2 responses. We hypothesize that mast cell degranulation would influence the Th1/Th2 balance in vivo and that this effect will not be observed in mice lacking mast cells. In this study, we show that when ovalbumin (OVA)‐specific CD4+ T cells adoptively transferred into normal mice are challenged with OVA in the presence of degranulation stimulus, these T cells proliferate in response to OVA but exhibit decreased IFNγ and increased IL‐4 production compared to control T cells primed in the absence of degranulation stimulus. In addition, when OVA‐specific CD4+ T cells are adoptively transferred into mast cell‐deficient mice and are challenged with OVA in the presence of degranulation stimulus, the decrease in IFNγ and increase in IL‐4 production are not observed. Moreover, when mast cell‐deficient mice are reconstituted with bone marrow‐derived mast cells, the adoptively transferred OVA‐specific CD4+ T cells proliferate in response to OVA and exhibit decreased IFNγ and increased IL‐4 production in the presence of degranulation stimulus as observed in normal mice. Altogether, these findings suggest that mast cells are essential for the degranulation‐induced shift from Th1 to Th2 responses.