Representation of marker proteins in individual OptiPrep® fractions. A. The individual lanes represent whole cell lysate (WL), enriched organelles (EO) and six individual fractions collected after density gradient centrifugation of PHA blasts expanded for 14 days. The blots were analyzed for the presence of known organelle marker proteins as indicated. One representative Western blot of four performed experiments with different T cell blasts is shown. B. An enrichment of FasL (as a marker protein for secretory lysosomes) is detected in fraction 2 of different lymphocyte subpopulations including CD4+ and CD8+ T cells, in vitro expanded human NK cells and the stably FasL-transfected Jurkat variant JFL.