Upon binding, B7:CD28 and B7:CTLA-4 provide costimulatory and coinhibitory signals, respectively, to T cells, thereby maintaining immune homeostasis or mediating immune disorder (Lindstein et al., 1989; Taube et al., 2012; Esensten et al., 2016; Xu et al., 2016). Here, CD80 is linked to immune system disorder.