CTSD and atherosclerosis: Trem2hi foamy macrophages possess a gene expression profile that partly overlaps with those of inflammatory macrophages and in addition express Lgals3, an atherosclerosis biomarker that promotes the differentiation of monocytes to macrophages and is linked to alternative macrophage activation and plaque evolution (151, 152), as well as expressing the Cd9 and Ctsd, the gene encoding cathepsin D. Cathepsin D is involved in the modification of LDL and facilitates phagocytosis of oxLDL by macrophages, which leads to the formation of foam cells (153).