STAT6 signaling attenuates interleukin-17-producing γδ T cells during acute Klebsiella pneumoniae infection

MH Bloodworth, DC Newcomb, DE Dulek… - Infection and …, 2016 - journals.asm.org
MH Bloodworth, DC Newcomb, DE Dulek, MT Stier, JY Cephus, J Zhang, K Goleniewska…
Infection and immunity, 2016journals.asm.org
ABSTRACT γδ T cells are prevalent at mucosal and epithelial surfaces and are a critical first
line of defense against bacterial and fungal pathogens. γδ17 cells are a subset of γδ T cells
which, in the presence of IL-23 and IL-1β, produce large quantities of interleukin-17A (IL-
17A), a cytokine crucial to these cells' antibacterial and antifungal function. STAT6, an
important transcription factor in Th2 differentiation and inhibition of Th1 differentiation, is
expressed at high levels in the T cells of people with parasitic infections and asthma. Our …
Abstract
γδ T cells are prevalent at mucosal and epithelial surfaces and are a critical first line of defense against bacterial and fungal pathogens. γδ17 cells are a subset of γδ T cells which, in the presence of IL-23 and IL-1β, produce large quantities of interleukin-17A (IL-17A), a cytokine crucial to these cells' antibacterial and antifungal function. STAT6, an important transcription factor in Th2 differentiation and inhibition of Th1 differentiation, is expressed at high levels in the T cells of people with parasitic infections and asthma. Our group and others have shown that STAT6 attenuates IL-17A protein expression by CD4+ T cells. By extension, we hypothesized that STAT6 activation also inhibits innate γδ17 cell cytokine secretion. We show here that γδ17 cells expressed the type I IL-4 receptor (IL-4R), and IL-4 increased STAT6 phosphorylation in γδ T cells. IL-4 inhibited γδ17 cell production of IL-17A. IL-4 also decreased γδ17 cell expression of IL-23R as well as Sgk1. To determine whether STAT6 signaling regulates γδ17 cell numbers in vivo, we used a model of Klebsiella pneumoniae in mice deficient in STAT6. We chose K. pneumoniae for our in vivo model, since K. pneumoniae increases IL-17A expression and γδ17 numbers. K. pneumoniae infection of STAT6 knockout mice resulted in a statistically significant increase in the number of γδ17 cells compared to that of wild-type mice. These studies are the first to demonstrate that γδ17 cells express the type I IL-4R and that STAT6 signaling negatively regulates γδ17 cells, a cell population that plays a front-line role in mucosal immunity.
American Society for Microbiology