B7-H1 is expressed by CD14⁺HLA-DR^lo monocytes in CTCL. (A-B) PBMCs from both normal donors (n = 23) and CTCL patients (n = 11) were stained with anti-CD14, anti–HLA-DR, and either an isotype control (closed histogram) or anti–B7-H1 (open histogram). The representative dot plot shown demonstrates a unique population of CD14⁺HLA-DR^lo cells present in CTCL patients. The frequency (percentage of total PBMCs) of HLA-DR^lo monocytes for normal donors and CTCL patients is shown in panel B. B7-H1 expression by the gated populations shown in panel A was determined. (C-D) B7-H1 expression (compared with an isotype control for each sample) by CD14⁺HLA-DR⁺ and CD14⁺HLA-DR^lo cells was analyzed (± 95% confidence interval is shown).