Experimental timeline. Tissue cage (TC) implantation and fluorogold (FG) injection was done 2 to 3 weeks prior to myelin oligodendrocyte glycoprotein (MOG) immunization. Agar was injected into the TC 2 days before immunization. Injection of Staphylococcus aureus (S. aureus) or saline was performed on day 4 postimmunization (pi). Animals were followed until day 8 of experimental autoimmune encephalomyelitis (EAE) or day 21 pi in case of clinically healthy animals. To monitor the infection, blood samples were taken throughout the whole experiment. Tissue was harvested from the optic nerve for histopathological analysis; retina was flat-mounted for quantification of retinal ganglion cells. Tissue cage fluid (TCF) was checked for the presence of bacteria.