A class II-restricted CD8ɣ13 T cell clone protects during Chlamydia muridarum genital tract infection.

The T cell response to chlamydia genital tract infections in humans and mice is unusual because the majority of antigen-specific CD8 T cells are not class I-restricted, referred to as "unrestricted" or "atypical". We previously reported that a subset of unrestricted murine chlamydia-specific CD8 T cells had a cytokine polarization pattern that included IFN-ɣ and IL-13. Here we investigated the transcriptome of CD8ɣ13 T cells, comparing them to Tc1 clones using microarray analysis. That study revealed that CD8ɣ13 polarization included IL-5 in addition to IFN-γ and IL-13. Adoptive transfer studies were performed with Tc1 clones and a CD8ɣ13 T cell clone to determine whether either influenced bacterial clearance or immunopathology during Chlamydia muridarum genital tract infections. To our surprise, an adoptively transferred CD8ɣ13 T cell clone was remarkably proficient at preventing chlamydia immunopathology while the multifunctional Tc1 clone did not enhance clearance or significantly alter immunopathology. Mapping studies with MHC class I- and class II-deficient splenocytes showed our previously published chlamydia-specific CD8 T cell clones are MHC class II-restricted. MHC class II-restricted CD8 T cells may play important roles in protection from intracellular pathogens that limit class I antigen presentation, or diminish CD4 T cell numbers or impair their function.