Figure 4.

LCL secrete MHCII⁺FasL⁺ exosomes. (A) Two LCL (designated “LCL-E” and “LCL-P”) were placed into fresh exosome-free media in the presence or absence of PMA/ionomycin. After 5 h (top panels) or 24 h (bottom panels), exosomes were isolated from culture supernatants as described in the section “Materials and Methods.” Purified exosomes were then incubated with anti-HLA-DR-coated beads as described in Figure 3. Beads were washed and stained with either anti-FasL or an isotype control antibody. Beads were coated with an appropriate isotype control antibody as the capture antibody did not display any FasL staining (data not shown). (B) Cells from above experiment were harvested, lysed, and probed for FasL and MHCII (HLA-DR) by immunoblot.