PGP and systemic lupus erythematosus: In 2000, Llorente et al. [70] studied P-gp expression and function in the peripheral blood lymphocytes isolated from 30 SLE patients and showed that the mean percentage of lymphocytes with high P-gp activity was increased as compared to the healthy controls; moreover, lymphocytes from SLE patients in clinical remission had a lower P-gp activity than those with active disease.