Clinical-scale generation of strongly CD83-expressing dendritic cells using extracorporeal photopheresis

Background: Many strategies are currently being pursued in order to generate mature dendritic cells (DC) to be used for immunotherapy. A potent anti-tumour influence by extracorporeal photopheresis has been documented for cutaneous T-cell lymphoma, and a major mechanism of action has been suggested to be generation of DC presenting tumour antigens. Purpose: To determine the potential of a simple clinical photopheresis protocol for large-scale development of mature DC. Methods: A standard monocyte-enriched leukapheresis preparation of 10(9)-10(10) cells was derived during each of five consecutive treatment sessions of a patient with cutaneous T-cell lymphoma. The cells were incubated overnight in autologous plasma with no addition of growth medium. Cell surface lymphocyte, monocyte and DC markers were determined using multi-colour flow cytometry. Results: We find signs of activation of the CD14+ monocytes, as well as the appearance of a minor population of mature DC negative for CD14 but with strong CD83 expression. Conclusions: With a procedure appropriate for routine clinical use, a total number of 10(6)-10(7) DC ready for patient reinfusion can be prepared within 24 h. Our findings indicate the need to further explore the capacity of photopheresis to stimulate cancer patients' anti-tumour defence reaction.