Resistance to experimental autoimmune encephalomyelitis in mice lacking the CC chemokine receptor (CCR)2

Abstract

Monocyte recruitment to the central nervous system (CNS) is a necessary step in the development of pathologic inflammatory lesions in experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. Monocyte chemoattractant protein (MCP)-1, a potent agonist for directed monocyte migration, has been implicated in the pathogenesis of EAE. Here we report that deficiency in CC chemokine receptor (CCR)2, the receptor for MCP-1, confers resistance to EAE induced with a peptide derived from myelin oligodendrocyte glycoprotein peptide 35-55 (MOGp35-55). CCR2(-/)- mice immunized with MOGp35-55 failed to develop mononuclear cell inflammatory infiltrates in the CNS and failed to increase CNS levels of the chemokines RANTES (regulated on activation, normal T cell expressed and secreted), MCP-1, and interferon (IFN)-inducible protein 10 (IP-10) as well the chemokine receptors CCR1, CCR2, and CCR5. Additionally, T cells from CCR2(-/)- immunized mice showed decreased antigen-induced proliferation and production of IFN-gamma compared with wild-type immunized controls, suggesting that CCR2 enhances the T helper cell type 1 immune response in EAE. These data indicate that CCR2 plays a necessary and nonredundant role in the pathogenesis of EAE.

Figure 1

Incidence of disease in CCR2^−/− and wild-type (WT) mice immunized with MOGp35–55. Groups of 5–10 mice were immunized with MOGp35–55 in CFA and received two intraperitoneal injections of Pertussis toxin. Results are expressed as mean disease score. This experiment is representative of n = 3.

Figure 2

Histology of CNS tissue from MOGp35–55-immunized mice. Hematoxylin and eosin–stained, formalin-fixed cerebellum (A and B) and spinal cord (C and D) from CCR2^+/+ (A and C) and CCR2^−/− mice (B and D) after immunization with MOGp35–55. Representative (n = 6 mice per group) perivascular inflammatory lesions (indicated by arrows) composed of mononuclear cells are shown in CCR2^+/+ brain and spinal cord sections. Note the absence of lesions and inflammatory cells in the sections from the brain and spinal cord of CCR2^−/− mice. Original magnification 240×.

Figure 3

Chemokine and chemokine receptor expression in brains of MOGp35–55-immunized mice. RNase Protection analysis on 5 μg of total RNA isolated from brains of CCR2^+/+ and CCR2^−/− animals at the indicated times (in days) after immunization. Unprotected probe for each chemokine (A) and each chemokine receptor (B), which run slightly higher than protected RNA species, is indicated in the first and/or last lane.

Figure 4

Ag-specific proliferative responses and cytokine production by spleen and LN cells from CCR2^+/+ and CCR2^−/− mice. Cells were isolated on days 8, 11, 20, 23, and 26 (spleen) and day 9 (LN; pooled from three mice per group) after disease induction and stimulated in vitro with MOGp35–55. Proliferative responses are shown as stimulation indices for each group responding to Ag concentration of 100 μg/ml. Cytokine concentration was measured from supernatants collected after 48 h (IFN-γ) or 72 h (IL-6) of in vitro culture with peptide (100 μg/ml).