Amount Used: ?1 Ug/106 cells Fresh BALB/c spleen cells were activated by incubation for 20 hours with PMA + ionomycin, then stained with either hamster IgG-FITC (as an isotype control) or hamster anti-mouse CD69-FITC. Large, activated cells were then gated and analyzed on a FACScan flow cytometer (BDIS, San Jose, CA).