Overall, these data suggest that there is a selective recruitment of CCR6+ IFNγ-secreting CD4+ memory T cells to the CSF that is increased in MS, that these cells are able to produce the encephalitogenic cytokine GM-CSF, and that these cells constitute the dominant CCR6+ CD4+ Th subset in the CSF in MS. Here, CSF2 is linked to myeloid sarcoma.