DELTA-AMINOLEVULINIC ACID-INDUCED FLUORESCENCE IN NORMAL HUMAN-LYMPHOCYTES

Endogenously generated protoporphyrin IX (PpIX) from exogenous delta-a minolevulinic acid (ALA) has the photodynamic capacity to inactive can cer cells of different origins. The aim of this study was to character ize the ability of normal lymphocytes to transform ALA into PpIX in or der to appreciate through further studies changes in pathologic lympho cytes. We investigated in this study PpIX synthesis by normal human ly mphocytes using a confocal laser microspectrofluorometer. Live lymphoc ytes were identified by monoclonal antibody fluorescent labeling. B an d T lymphocytes synthesized PpIX (80-100 counts), with a maximum being reached after 4 h ALA incubation. When T subpopulations of lymphocyte s were labeled, T4 and T8 changes in fluorescence kinetics were simila r, reaching a maximum after 5 h ALA incubation. The influence of monoc lonal antibody labeling on this delayed increase for maximum fluoresce nce is considered. Phytochemaglutinin (PHA, incubation for 72 h) lymph ocyte stimulation induced a 100% increase in PpIX fluorescence for T l ymphocytes, whereas pokeweed mitogen activation produced an increase o f about 50% in the B- or T-lymphocyte signal. Finally, the scanning fl uorescence image clearly indicated the inhomogeneity of cytoplasmic AL A-induced PpIX fluorescence, which was probably due to the distributio n of mitochondria. The influence of this heterogeneity on PpIX photose nsitivity effects is discussed. (C) 1997 Elsevier Science S.A.