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Figure 7 | Journal of Neuroinflammation

Figure 7

From: TGFβ signalling plays an important role in IL4-induced alternative activation of microglia

Figure 7

Proposed model for the role of TGFβ in IL4-induced alternative microglia activation. IL4 induces expression of the alternative activation markers Ym1 and Arg1 via the IL4Rα-Stat6 pathway. TGFβ binds to its receptors TGFβ type I and type II, which form a heteromeric complex and initiate Smad-dependent and Smad-independent pathways. Exogenous TGFβ1 enhances IL4-induced Ym1 and Arg1 expression either by a direct effect on Ym1/Arg1 promoter activity or indirectly by up regulating the IL4Rα through activation of the MAP kinase (Smad-independent) pathway. Furthermore, IL4 treatment alone increased endogenous TGFβ2 expression and secretion. Autocrine TGFβ2 in turn might be able to enhance IL4-induced Arg1 expression by using similar signalling mechanisms to exogenous TGFβ1.

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