Assuming that IgG infusion in the CNS could induce immune cell infiltration in the rat CNS, we looked for the presence of CD8+, CD45RA+, and CD45+ cells and MPO+ (neutrophil) in the brain, spinal cord, and optic nerve of the NMO-rats (n = 4) and the Control-rats (n = 4) (D7) by using IHC. The gene discussed is MPO; the disease is neuromyelitis optica.