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, 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.
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, versus 0.50% in healthy donors, n=7, p<0.0001). The CD209+ mDC numbers only accounted for 3.28% out of total mDCs in patients compared to 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=0.103) and by 6.4-fold at 6 months (n=9, p=0.100). 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 CELLEX photopheresis system is effective for treating L-CTCL patients like the UVAR XTS system, and in vivo generated Mo-DCs increase following ECP.

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