TARGETING ACTIVATED LYMPHOCYTES WITH PHOTODYNAMIC THERAPY - SUSCEPTIBILITY OF MITOGEN-STIMULATED SPLENIC LYMPHOCYTES TO BENZOPORPHYRIN DERIVATIVE (BPD) PHOTOSENSITIZATION

Benzoporphyrin derivative monoacid ring A (BPD), a hydrophobic chlorin -like porphyrin derivative, which fluoresces strongly at 690 nm, may h ave potential for both oncologic and nononcologic applications in phot odynamic therapy (PDT). To study the influence of cellular characteris tics on the uptake of BPD, the murine tumor cell line (P815), and in v itro and in vivo concanavalin A (Con A)-stimulated and unstimulated mu rine splenic lymphocytes were incubated with 2 mu g/mL BPD at 37 degre es C for 0-60 min. At various times, cells were lysed and the amount o f BPD taken up by the cells was quantified by fluorescence measurement s. The subsets of cells taking up BPD were analyzed using a panel of m onoclonal antibodies and the Coulter XL(R) fluorescence-activated cell sorter. Furthermore, Con A-stimulated and unstimulated spleen cells w ere incubated with 0-50 ng/mL of BPD for 1 h prior to exposure to red light (7.2 J/cm(2)). Cell survival 24 h post-PDT was measured by the M TT assay. We found that the rapidly dividing tumor cell line and mitog en-stimulated murine T cells (mainly CD4(+)/IL-2R(+)) took up signific antly more BPD (5-10-fold) than do unstimulated splenic lymphocytes. I ncreased BPD uptake correlated with greater photoinactivation when the se cells were exposed to light at a wavelength of 690 nm. These findin gs suggest that activated cells of the immune system may be a target f or photoinactivatien by BPD.