Phenotype switching by inflammation‐inducing polarized Th17 cells, but not by Th1 cells

Abstract

Analyses of inflammation inducing Th cells revealed that a portion of these cells express both IFN‐γ and IL‐17, suggesting that Th1 and/or Th17 may switch their phenotype. Here, we examined phenotype retention in a system in which polarized Th1 or Th17 cells specific against hen egg lysozyme (HEL) induce ocular inflammation in recipient mice expressing HEL in their eyes. Whereas no switching to Th17 was detected in Th1 recipient eyes, substantial proportions of transferred Th17 expressed IFN‐γ, or both IFN‐γ and IL‐17 in Th17 recipient eyes. The phenotype switch of Th17 cells increased with time and was attributed to exposure to IL‐12 that is expressed in the inflamed eyes. Incubation in vitro with Th1 polarizing cocktail (IL‐2+IL‐12) converted most Th17 into IFN‐γ or IFN‐γ/IL‐17 expressing cells, but no reciprocal conversion was noted with Th1 cells. Furthermore, whereas Th1 cells did not express ROR‐γt following incubation with Th17 polarizing cocktail, Th17 expressed T‐bet following incubation with Th1 cocktail. Thus, polarized Th1 cells fully retain their phenotype, while Th17 switch and express IFN‐γ or both IFN‐γ and IL‐17, as well as T‐bet, following exposure to IL‐12.This study is supported by NEI/NIH intramural program.