Fc receptor-positive cells in remyelinating multiple sclerosis lesions

The capacity for spontaneous remyelination in cases of multiple sclerosis (MS) is limited and lesions are not fully repaired. Recent evidence has shown that oligodendrocyte precursor cells and immature oligodendrocytes (OPC/iOligs) are preserved in MS lesions. Induced differentiation of these cells into myelinating cells may ultimately lead to a novel remyelination therapy. A previous study showed that the γ chain of immunoglobulin Fc receptors (FcRγ), expressed in OPC/iOligs, is essential for their differentiation. Whether FcRγ is expressed in preserved OPC/iOligs within MS lesions, however, remains uncertain. In the present study, we examined 10 autopsy cases of MS for the expression of FcRγ both in remyelinating areas and demyelinated plaques. The expression of FcRγ was confirmed in both OPC/iOligs and microglia in MS lesions. Statistical analysis showed that the density of FcRγ-positive OPC/iOligs was approximately 3 times greater in remyelinating areas compared with demyelinated plaques; the opposite was true of FcRγ-positive microglia. The distribution of FcRγ-negative OPC/iOligs did not differ between the 2 types of lesions. Thus, an increase in FcRγ-positive OPC/iOligs and a decrease in FcRγ-positive microglia, but not in FcRγ-negative OPC/iOligs, are associated with spontaneous remyelination in MS brains, suggesting a possible role for FcRγ in the induction of remyelination.