The use of ovalbumin as an antigen - (Jun/27/2010 )

In this paper I'm reading, the researchers were looking at IFN-y secretion (via ELISA) from CpG DNA +Ovalbumin exposed mice. CpG is the known PAMP for TLR9 and elicits a Th1 like response. Ovalbumin, from what I've read, induces a Tc response. Why would the researchers use ovalbumin for this and not just CpG DNA?

I guess my real question is "what is the purpose of ovalbumin sensitizing mice?"