ECP-induction of costimulatory molecules DC-LAMP and class II MHC was determined by flow cytometric analysis of processed monocytes. Monocytes were from (A) CTCL, (B) normal subjects, and (C) GVHD patients. Forward and side scatter gating, confirmed by CD11c and CD14 staining, was used to identify the monocyte population. The cells were fixed and permeabilized and the monocyte/DC population was stained for HLA-DR (FITC) on the membrane and CD83 or DC-LAMP (phycoerythrin, PE) in the cytoplasm to identify differentiating DCs. Two-color membrane staining for CD80 (FITC) and CD86 (PE) was used to identify expression of costimulatory molecules. Results are presented from 1 representative subject per group.