Role of Natural Killer and Dendritic Cell Crosstalk in Immunomodulation by Commensal Bacteria Probiotics

Figure 1

Bi-directional activation between dendritic cell and natural killer (NK) cells in the presence of commensal bacteria. Immature dendritic cells (iDC) are activated and matured by commensal bacteria, for example, lactic acid bacteria (LAB). These LAB-activated mature dendritic cells (DC) produce cytokines able to activate NK cell cytotoxicity and induce their proliferation. Activated NK cells can in turn, via the release of relevant cytokines, recruit (GM-CSF) and activate iDC (TNF-α and IFN-γ). Alternatively, activated NK cells can exert an editing of DC by killing some of the iDC. At the same time, the early release of IFN-γ by NK cells interacting with LAB-activated DC, most likely in secondary lymphoid organs such as the mesenteric lymph nodes, is critical for shaping the following adaptive immune response toward a type 1 T cell response. Remarkably, some LAB display opposite outcomes and could hamper T cell type 1 polarization.