Following BTV infection or vaccination, sheep develop both anti-virus antibody (which may include neutralizing antibody) and a cellular immune response. Yet, it still is unclear what aspects of the response are most critical in preventing infection and disease from this virus. This is, in part, the result of a lack of knowledge of all of the viral virulence factors. However, with the current work involving subunit vaccines and the efforts to more carefully characterize virulence factors and tissue tropism, there will be a more thorough understanding of the immunobiology of the Bluetongue virus.