NPC1 and systemic lupus erythematosus: Additionally, assessing the expression profiles of the aforementioned key genes in various cell types revealed that ABCB1, AKR1C3, and NPC1 were primarily expressed in NK cells and downregulated in SLE; IFIH1 and SCO2 were mainly expressed in monocytes and macrophages and were upregulated in SLE; and GADD45A was mainly expressed in naive CD8+ T cells and effector memory CD8+ T cells, exhibiting downregulation in SLE (Figure 7D).