Uterine Chlamydia suis and C. trachomatis infections induce strong pathology in pigs. Precise analysis of the adaptive immune response to porcine chlamydia infections. C. suis and C. trachomatis induce homo- and heterologous IFN-γ+TNF-α+ CD4 T cells. Potential for cross-protection between the two chlamydia species. Pigs represent a valuable large animal model for vaccine development.