The immune system is incredibly complicated. Any discussion of how it works can be derailed into myriad asides and explanations. Nonetheless, I shall attempt to be brief and to the point.
For some infections, such as those caused by some viruses, fever is a normal part of the infection fighting process. But what induces the fever? One possibility is a protein called RIG-1 (retinoic acid inducible gene protein one). This protein is a helicase which recognizes double stranded RNA (dsRNA). dsRNA is often found in viruses but not in uninfected animal cells. This ensures that RIG-1 is only active in infected cells.
RIG-1 causes the release of pro-interleukin, and also activates the transformation of pro-interleukin into interleukin-1. Interleukin-1 was one of the earliest cytokines (proteins which serve important roles in the immune system as well as in cell signaling) discovered. Among other effects, interluekin-1 causes fever.
Prior to the study by Dr. Michael Bscheider and Dr. Olaf Gross, RIG-1 was known to ensure the release of interferon, a type of cytokine responsible for gearing up the cell’s killer cells. These in turn, are responsible for killing infected cells. Now it appears that RIG-1 also affects other cytokines which cause the fever.
As I alluded to in the beginning, there are a host of factors involved in the immune system, many of which play multiple roles. Inducing fever, albeit indirectly, can now be added to RIG-1's repertoire.