In accordance with the attenuated ocular inflammation seen in the C4 KO mice after immunization, our ex vivo IRBP-specific recall experiments and ocular CD4+ T cell infiltration analysis showed reduced development of IRBP-specific IFNγ- and IL-17-producing T cells and decreased numbers of infiltrating CD4+ cells in the eyes of C4 KO mice in EAU. Here, IL17A is linked to inflammation.