PEPD and lupus nephritis: Prolidase-deficient mice also demonstrate an activated T cell phenotype and elevated serum IgA, with glomerular immune complex deposition reminiscent of early human lupus nephritis (44), mimicking the phenotype in a subset of PD patients (7, 8, 11, 45) and confirming, to our knowledge, for the first time, the direct association of autoimmunity and PD.