C1QB and myeloid sarcoma: A recent single-nucleus transcriptome analysis of chronic MS lesions identified two subsets of microglia—one associated with phagocytosis, enriched in foam-cell differentiation and lipid storage genes, and a second subset associated with iron metabolism, enriched among others in genes encoding heavy and light chain ferritin, and complement component C1 complex (C1QA and C1QB) [12].