Abstract: Objective To study apoptosis and dendritic cells (DC) in skin lesions of mycosis fungoides and their relation to the disease course. Methods Monoclonal antibody (mAb) and immunohistochemical multiple staining were used to detect the expression of special antigen on the surface of DC, which indicating an immature DC (iDC). Apoptotic cells were detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) test. Results In the lesions of patch/plaque-stage (PS) a few apoptotic cells were found in Pautrier's microabscesses and in the dermal T cell infiltrated area, and large number of apoptotic tumor cells were observed in the dermal T cell infiltrated area of tumor stage (TS) (P<0.01), especially densely interspersing in lower dermis. Immunohistochemical study showed that there were large amount of immature DC and apoptotic tumor cells phagocytized and surrounded by immature Lag⁺ and CD1a⁺ DC in the deep dermis. This phenomenon was rarely found in the lesions of plaque stage. Conclusions The appearance and increasing apoptosis in MF lesions may be an important pathological character of MF in progressive stage. The phenomenon of apoptotic tumor cells surrounded and phagocytized by iDC suggests the crosspresenting in inducing antitumor immunity, which may induce antitumor immunologic tolerance.

Key words: Mycosis fungoides, Dendritic cells, Apoptosis