Figure 3: Hypothetical responses of Th1 and Th2 cells in regulatory (A: see detail in the section of goblet cell metaphase from Clara and ciliated cells) and inflammatory (B) subtypes proposed by Liu [107]. IL-4 and IL-12 are classic Th2 cell–polarizing and Th1 cell–polarizing factors, respectively. OX40L, which contributes to the differentiation, proliferation and actibation of T cells, from DCs together with IL-4 promotes TNF-α but inhibits IL-10 production from inflammatory Th2 cells or inflammatory Th1 cells induced by OX40L together with IFNα/β from DCs. Injury of epithelial cells or epithelial cell stimulated with environmental factors (TLRLs) reacting with TLR on epithelium trigger to produce TSLP from mucosal epithelium, leading to expression of TSLPR on DCs. TSLP initiates the innate phase of allergic immune responses by activating immature DCs. TSLP-activated mDCs lead to the adaptive phase of allergic immune responses. TSLP-activated DCs expressing OX40L, which induce the inflammatory Th2 cells. In addition, TSLP was shown to be able to directly act on naïve CD4+ T (Th0) cells to promote Th2 differentiation and/ or IL-4 secretionin vivo and in vitro. On the other hand, DCs stimulated with TLRLs produce IFNα/β in the innate phase, leading to the development of the adaptive phase of Th1 responses.
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