Mapping the MHC restriction of murine T cell hybridomas to Francisella tularensis (2006)

Undergraduate: Alicia Cawlfield

Faculty Advisor: Jeffrey Frelinger
Department: Biology

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Francisella tularensis, which is a small, facultative intracellular bacterium, is highly pathogenic to humans and causes the disease known as tularemia. The CDC has listed F. tularensis as a category A agent for biological warfare because it is easily transmitted to humans and has a high survival rate in the environment. In spite of this, the immune response to F. tularensis has not been adequately studied. In this study, an attenuated live vaccine strain was used as a model for studying the T cell immune response.
Two main subsets of T cells interact with different classes of MHC molecules on antigen-presenting cells in the body. MHC class I molecules present endogenous proteins, as produced during infection. MHC class II molecules present extracellular proteins taken up by the cell. These T cell subsets produce different responses in the body. Antibodies that react with MHC class I or class II molecules were used in this study. The function of these antibodies was to inhibit the activation of a panel of mouse T cell hybrids according to their MHC recognition. Eighty-one T cell hybrids were tested for their MHC recognition using killed F. tularensis, and 74 interact with class II. The data show that most T cell hybrids that recognize killed F. tularensis interact with MHC class II as predicted. These data show that a vaccine created with whole killed F. tularensis is ineffective because it triggers only part of the protective immune response to the pathogen.