CCR2⁺CCR5⁺ T cells produce matrix metalloproteinase-9 and osteopontin in the pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the CNS that is presumably mediated by CD4⁺ autoimmune T cells. Although both Th1 and Th17 cells have the potential to cause inflammatory CNS pathology in rodents, the identity of pathogenic T cells remains unclear in human MS. Given that each Th cell subset preferentially expresses specific chemokine receptors, we were interested to know whether T cells defined by a particular chemokine receptor profile play an active role in the pathogenesis of MS. In this article, we report that CCR2⁺CCR5⁺ T cells constitute a unique population selectively enriched in the cerebrospinal fluid of MS patients during relapse but not in patients with other neurologic diseases. After polyclonal stimulation, the CCR2⁺ CCR5⁺ T cells exhibited a distinct ability to produce matrix metalloproteinase-9 and osteopontin, which are involved in the CNS pathology of MS. Furthermore, after TCR stimulation, the CCR2⁺CCR5⁺ T cells showed a higher invasive potential across an in vitro blood-brain barrier model compared with other T cells. Of note, the CCR2⁺CCR5⁺ T cells from MS patients in relapse are reactive to myelin basic protein, as assessed by production of IFN-γ. We also demonstrated that the CCR6^-, but not the CCR6⁺, population within CCR2⁺CCR5⁺ T cells was highly enriched in the cerebrospinal fluid during MS relapse (p < 0.0005) and expressed higher levels of IFN-γ and matrix metalloproteinase-9. Taken together, we propose that autoimmune CCR2⁺CCR5⁺ CCR6^- Th1 cells play a crucial role in the pathogenesis of MS.