PGP and systemic lupus erythematosus: In light of our previous findings, we designed an in vitro experiment to elucidate whether there are P-gp inhibitors, such as CTX, mycophenolic acid (MPA) and emodin, which affect the efflux-function of P-gp in the lymphocytes of SLE patients (13–15) Three patients with active SLE and high expression levels of active P-gp in their peripheral lymphocytes were selected.