CD27 and systemic lupus erythematosus: Unlike transitional-phenotype B cells, rapid reconstitution of CD27+ B cells correlates with clinical relapse of B cell-depleted SLE and rheumatoid arthritis patients (Leandro et al., 2006; Anolik et al., 2007; Roll et al., 2008; Moller et al., 2009; Nakou et al., 2009; Iwata et al., 2011a).