CD209+ monocyte‐derived myeloid dendritic cells were increased in patients with leukemic cutaneous T‐cell lymphoma undergoing extracorporeal photopheresis via the CELLEXTM system

Abstract

We previously reported that myeloid dendritic cells (mDC) were increased in patients with leukemic cutaneous T-cell lymphoma (L-CTCL) following extracorporeal photopheresis (ECP) using the Therakos UVAR XTS™ system. We now assessed monocyte-derived mDCs (Mo-DCs) in L-CTCL patients treated with the CELLEXTM photopheresis system. CD209, a transmembrane receptor, was used to define Mo-DCs. Peripheral blood samples from baseline pre-ECP and at Day 2, 1month, 3months, and 6months post-ECP were analyzed by flow cytometry for Lin- HLA-DR+ CD123+ plasmacytoid dendritic cells (pDCs), Lin- HLA-DR+ CD11c+ mDCs, and CD209+ mDCs. The expression of CD209 mRNA was assessed by real-time PCR. At baseline, 7 of 19 patients had lower than normal mDCs, and all patients had lower than normal CD209+ mDCs in peripheral blood mononuclear cells (0.005% in patients, n=19, vs 0.50% in healthy donors, n=7, P<.0001). The CD209+ mDC numbers only accounted for 3.28% out of total mDCs in patients compared with 66.51% in healthy donors. After treatment, the CD209+ mDC numbers showed increasing trends in patients. The average absolute numbers of CD209+ mDCs went up by 4.8-fold at 3months (n=10, P=.103) and by 6.4-fold at 6months (n=9, P=.100). CD209 mRNA expression went up in two patients responsive to therapy, parallel to CD209+ mDC numbers. L-CTCL patients achieved 70% overall clinical response rate (7/10) following ECP therapy with the CELLEXTM system. Our results suggest that the CELLEXTM photopheresis system is effective for treating L-CTCL patients like the UVAR XTS™ system, and in vivo-generated Mo-DCs increase following ECP.