GPR34 and myeloid sarcoma: This elevation may reflect an increase in border-associated macrophages (BAM)/CSF macrophages as CSF transcriptomic analyses revealed elevated expression of BAM/microglial markers (including TREM2, LYVE1, and GPR34) in CD14+CD16+ monocytes.20,21 This age-related shift may represent one pathway linking aging to altered inflammatory responses in MS, possibly accounting for certain age-related changes in disease manifestation and potentially support a gradual shift to compartmentalization of inflammation.22