Interleukin-6 expression in human multiple sclerosis lesions.

The present study investigated interleukin-6 (IL-6) expression in 36 multiple sclerosis (MS) cases by immunocytochemistry. The numbers of IL-6 expressing cells were correlated to the stage of demyelinating activity and the pattern of oligodendrocyte pathology. IL-6 positive cells were identified as macrophages and astrocytes by morphological criteria. Approximately 10-17% of the astrocytes and up to 2% of the macrophages within the lesion expressed IL-6. Highest numbers of IL-6 expressing cells were found in inactive demyelinating lesions. There was a significant increase of IL-6 positive cells in lesions with oligodendrocyte preservation, whereas absence of IL-6 expression correlated with oligodendrocyte loss. These observations indicate a possible important role for IL-6 in oligodendrocyte protection and survival in MS lesions.