Fig. 1.

Possible interaction of DC, NK and γδ T cells in an innate immune response. The figure shows three major cellular components of the innate immune system. It appears that each of the cellular components might initiate innate responses individually. Mostly because all the cell types express TLR, hence are capable of sensing pathogens. DC, upon encounter with pathogens or receiving signals from the periphery through chemokines, produce cytokines such as IL-1, IL-2, IL-12, IL-15 and IL-18, which are important activators of NK cells. NK cells in turn respond by secreting more cytokines, particularly TNFα, IFNγ, GM-CSF and HMGB1 that have a regulatory effect on DC and an activating effect on γδ T cells. Further, the NK cells proliferate in response to DC cytokines and enhance cytotoxicity against virus infected cells. In addition to cytokines secreted by NK cells γδ T cells also, secrete TNFα and GM-CSF that affect the DC activation leading to maturation and enhanced expression of MHC class I and II molecules and subsequent antigen presentation. The interplay depicted here account for the effective role played by these cells to counteract infection before it spreads within the host. However, the efficacy with which these mechanisms are executed remains largely unknown in large animal species, since viruses such as FMDV manage to efficiently replicate in swine and cause immunosuppression.