CD19 and systemic lupus erythematosus: In both healthy controls and SLE patients, CD64 was expressed constitutively on circulating CD14+ monocytes and CD11c+ myeloid dendritic cells (MDCs) (Figure 1b) In contrast, CD64 was expressed at low levels on peripheral blood CD16+ neutrophils, and no expression was found on CD3+ T cells or CD19+ B cells (Figure 1b).