Pigeon fever is an equine disease caused by the bacteria Corynebacterium pseudotuberculosis . These gram-positive bacteria infect horses in the Western part of the United States and lead to three types of disease manifestations: external abscesses on the pectoral region, internal abscesses, or ulcerative lymphangitis (Spier 2006). The overarching goal of this research is to gain a better understanding of the equine immune response to this bacteria so we can create a successful vaccine, which is essential in protecting the equine community. One question we are studying is whether the type of T-helper cell responses, TH1 or TH2, determines the manifestation of the disease. This summer, we started a new mouse model to study a potential vaccine. We also ran tests on our previous mouse experiments to observe antibody levels. Using mice helps us effectively study Pigeon Fever because the mice are genetically identical, inexpensive, and easy to handle compared to horses. Our lab uses two inbred strains of mice: BALB/c, which show a TH2 response, and C57Bl/6, which show a TH1 response (Mills 2000). Both strains can provide data to provide a thorough understanding about the immune response to the bacteria to ultimately create a vaccine. The mice are immunized and then challenged with the bacteria. Using ELISAs, antibody levels are measured and the disease severity caused by the bacteria is determined. By learning about the type of antibody response, we can gain a better understanding of the bacteria which will ultimately lead to creating an effective vaccine.