MHC class II-restricted Chlamydia-specific CD4 T cell clones recognize infected upper reproductive tract epithelial cells as early as 12 hours post infection. The timing and degree of T cell activation are dependent on the interferon milieu. Different interferons have different effects on T-cell activation interferon IFN-β blunts IFN-γ induced up regulation of epithelial cell surface MHC class II and T cell activation. A subset of CD4 T-cells that was especially good at clearing Chlamydia infections from the genital tracts of infected mice was found to express the genes Casd1 and Plac8. The mouse Casd1 genes shares some 95 percent identity with the human gene. The differential expression of either Plac8 or Casd1 in COD cells in response to an infection of epithelial tissue provides a ready methodology for the identification of individuals exposed to epithelial infections and a tool for developing vaccines against pathogens that infect epithelial tissue.
