Extensive research revealed diverse characteristics of AO rats which, in contrast to characteristics of DA rats, actually contribute to the resistance to the induction of autoimmune diseases, and are described both in periphery (for example, low IL-2, IFN-γ, TNF, IL-17, inability to expand Th1 response, low proportion of CX3CR1+ NK cells in draining lymph nodes) [104,105], as well as in target organs (i.e., higher expression of chemokine CXCL12 and impaired expression of chemokine ligand CCL2 in spinal cord tissue, low expression of heat-shock protein 47 in joint tissue) [106,107,108]. The gene discussed is CCL2; the disease is autoimmune disease.