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Keywords:

  • bovine;
  • γδ T cell;
  • interferon-γ;
  • major histocompatibility complex class II;
  • Mycobacterium bovis

Summary

Evidence suggests that γδ T cells form part of the innate immune response to Mycobacterium bovis infection. Dendritic cells (DCs) are capable of secreting high levels of interleukin-12 (IL-12) following infection with mycobacteria and can induce interferon-γ (IFN-γ) secretion by natural killer and γδ T cells We investigated the innate interactions occurring between WC1+γδ T cells and M. bovis-infected DCs. Following coculture with M. bovis-infected DCs, secretion of IFN-γ and expression of CD25 and major histocompatibility complex class II on WC1+γδ T cells were significantly enhanced. Reciprocal enhancement of IL-12 secretion by the DCs was also observed and this interaction was found to be contact dependent. We hypothesize that there is an early, transient signal between the WC1+γδ T cells and the DCs, which promotes the synthesis of biologically active IL-12, and which is dependent upon cell–cell contact. Reciprocal signals including IL-12 are then delivered to WC1+γδ cells, which leads to the enhanced secretion of IFN-γ, and the up-regulation of activation markers and antigen presentation molecules by the WC1+γδ T cells. These interactions are likely to form a critical part of the T helper type 1-conditioning response of DCs to M. bovis.