Existing research provides some support: PSAP reduces the proportion of CD8+ T cells in PBMC [63], and hydroxychloroquine (HCQ), an immunomodulatory drug used for RA and systemic lupus erythematosus (SLE), binds to saposin B (a cleavage product of PSAP) [64]. This evidence concerns the gene PSAP and systemic lupus erythematosus.