Infection with bacterial pathogens can disrupt the intestinal mucosa that maintains a healthy immune system while keeping bacteria at bay. Using a model of oral infection with a murinized form of Listeria monocytogenes (Lm), our lab has identified a γδ T cell population that forms bona-fide memory and provides protection from re-infection. Since the precise mechanism of activation of most γδ T cells has remained elusive, we investigated the requirements for antigen presenting cells (APCs) in the activation of Lm-induced memory γδ T cells. Here, we show that several cells in the mesenteric lymph node (mLN), including dendritic cells (DCs), inflammatory monocytes and granulocytes, can act in conjunction to activate γδ T cells to express IL-17A, IFN-γ or both and induced their proliferation. This activation was largely cell contact dependent, but was augmented by soluble factors at the peak of primary and secondary γδ T cell responses, mainly by IL-1β but partially by IL-2 and IL-23. Moreover, using confocal microscopy we were able to image Lm-induced γδ T cells interacting with DCs and inflammatory monocytes in the interfollicular area of the mLNs soon after Lm challenge infection. We believe these results not only advance the understanding of γδ T cell biology, but also provide novel strategies to design protective vaccines for the intestinal mucosa.
- Copyright © 2013 by The American Association of Immunologists, Inc.