Expression of specific chemokines and chemokine receptors in the central nervous system of multiple sclerosis patients

Abstract

Chemokines direct tissue invasion by specific leukocyte populations. Thus, chemokines may play a role in multiple sclerosis (MS), an idiopathic disorder in which the central nervous system (CNS) inflammatory reaction is largely restricted to mononuclear phagocytes and T cells. We asked whether specific chemokines were expressed in the CNS during acute demyelinating events by analyzing cerebrospinal fluid (CSF), whose composition reflects the CNS extracellular space. During MS attacks, we found elevated CSF levels of three chemokines that act toward T cells and mononuclear phagocytes: interferon-gamma-inducible protein of 10 kDa (IP-10); monokine induced by interferon-gamma (Mig); and regulated on activation, normal T-cell expressed and secreted (RANTES). We then investigated whether specific chemokine receptors were expressed by infiltrating cells in demyelinating MS brain lesions and in CSF. CXCR3, an IP-10/Mig receptor, was expressed on lymphocytic cells in virtually every perivascular inflammatory infiltrate in active MS lesions. CCR5, a RANTES receptor, was detected on lymphocytic cells, macrophages, and microglia in actively demyelinating MS brain lesions. Compared with circulating T cells, CSF T cells were significantly enriched for cells expressing CXCR3 or CCR5. Our results imply pathogenic roles for specific chemokine-chemokine receptor interactions in MS and suggest new molecular targets for therapeutic intervention.

Figure 1

IP-10 concentration correlates with leukocyte count in CSF of MS patients during acute attacks. The scatter diagram shows the relationship between concentration of IP-10 and leukocyte count in the CSF of MS patients (n = 38). Each closed square represents data from one patient. The best-fit line is shown. Pearson r value = 0.4925; two-tailed P = 0.0017. CSF, cerebrospinal fluid; IP-10, interferon-γ–inducible protein of 10 kDa; MS, multiple sclerosis.

Figure 2

Inflammatory demyelination in an active MS lesion. (a) Hematoxylin–eosin histochemistry was combined with Luxol fast blue, which stains myelin blue. This technique reveals a zone of demyelination, abundant perivascular inflammation (arrowheads), and an irregular, hypercellular lesion edge (LE), below which is normal white matter. ×80. (b) Within the lesion, myelin debris, stained blue with Luxol fast blue, is evident within phagocytic macrophages (arrowheads), indicating active demyelination. ×170.

Figure 3

Expression of CXCR3 and IP-10 in MS lesions. (a) Numerous CXCR3-immunoreactive cells are present in perivascular inflammatory infiltrates in an acute MS lesion in white matter surrounding a ventricle (vent). ×80. (b) CXCR3-immunoreactive cells in a perivascular infiltrate exhibit similar morphology and distribution to CD3-positive T cells (c). ×170. (d) Immunohistochemistry for IP-10 reveals staining of the cell bodies of reactive astrocytes (arrows). Intense staining is also seen in processes, consistent with astrocytic end-feet that extend to, and surround, a blood vessel. Scattered reactive astrocytes in the surrounding parenchyma also express IP-10 (arrowheads). ×300. CXCR3, type 3 CXC chemokine receptor.

Figure 4

CCR5 expression by multiple leukocyte populations in an active MS lesion. (a) Near the lesion edge (LE), CCR5 immunohistochemistry reveals scattered elongated process-bearing cells consistent with reactive microglia (arrows) and small, round lymphocytic perivascular cells (arrowheads), while the lesion (the portion of the panel to the right of the lesion edge) contains numerous CCR5-positive phagocytic macrophages. ×170. (b) CCR5-immunoreactive cells in the lesion center are primarily phagocytic macrophages (arrows). ×170. CCR5, type 5 CC chemokine receptor.

Figure 5

Expression of CCR1 and CCR3 in MS lesions. (a) CCR1 immunohistochemistry in an active lesion reveals small, round cells in the perivascular space. Immunoreactive cells are morphologically consistent with infiltrating lymphocytes. ×170. (b) Small, round CCR3-immunoreactive cells in a highly active lesion are scattered through perivascular and parenchymal sites. ×170.