Chemokine receptors on infiltrating leucocytes in inflammatory pathologies of the central nervous system (CNS)

Haematogenous leucocytes enter the central nervous system (CNS) during diverse disorders of varied aetiologies. Understanding the trafficking cues that mediate CNS leucocyte infiltration might promote the development of flexible and selective means to modulate inflammation to achieve clinical benefit. The trafficking machinery of leucocytes has been elucidated during the past decade and consists of cell-surface adhesion molecules, chemoattractant cytokines (chemokines) and their receptors. Recent work in our laboratory characterized chemokine receptors found on T lymphocytes and monocytes in brain sections from subjects with one pathological subtype of multiple sclerosis (MS), an immune-mediated inflammatory demyelinating disease. In these tissues, the types 1 and 5 CC chemokine receptors (CCR1 and CCR5) were detected on perivascular monocytic cells whereas only CCR5 was present on parenchymal macrophages. The type 3 CXC chemokine receptor (CXCR3) was present on virtually all CD3-positive T cells. In the current study, we evaluated the expression of these receptors on the infiltrating cells present in cases of other inflammatory CNS disorders including those of dysimmune, infectious, neoplastic, and vascular aetiology. Perivascular and parenchymal monocytic cells expressed CCR1 in all cases and CXCR3 was consistently present on a substantial proportion of CD3+ T cells. The occurrence of CCR5 on parenchymal macrophages was much less uniform across the varied disorders. These data implicate CCR1 in monocyte infiltration of the CNS and are consistent with reports of studies in CCR1-deficient mice. CXCR3 is also likely to play a role in accumulation of T cells in the inflamed CNS. By contrast, our findings suggest that regulation of CCR5 on phagocytic macrophages may be contingent on the lesion environment.