ICOS and systemic lupus erythematosus: We examined whether in vivo treatment with PD-L1 expressing MDSCs might have more beneficial effects on renal histopathology and autoantibody production in one animal model of lupus, Roquinsan/san mice, in which the sanroque mutation disrupts a repressor of ICOS, an essential co-stimulatory molecule for follicular helper T cells (Tfh cells), resulting in excessive formation of Tfh cells and germinal centers (GC) (12, 13).