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

Background/Purpose 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 CELLEX TM photopheresis system. CD209, a transmembrane receptor, was used to define Mo‐DCs. Methods Peripheral blood samples from baseline pre‐ECP and at Day 2, 1 month, 3 months, and 6 months 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. Results 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 3 months (n = 10, P  = .103) and by 6.4‐fold at 6 months (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 CELLEX TM system. Conclusions Our results suggest that the CELLEX TM photopheresis system is effective for treating L‐CTCL patients like the UVAR XTS ™ system, and in vivo ‐ generated Mo‐DCs increase following ECP .