CD19 and systemic lupus erythematosus: The percentage of CD19+PLT+ correlated positively with concentrations of IgG and IgA levels and correlated negatively with concentrations of IgM in SLE patients (Figures 2(a)–2(c)), though not with HD (r = 0.22, p = 0.52 for IgM; r = 0.08, p = 0.81 for IgA; and r = 0.31, p = 0.39 for IgG).