Immunofluorescent Staining: Cells from BALB/c mesenteric lymph nodes were double-stained with anti-mouse CD8a-FITC and anti Mouse CD4-R-PE (clone GK1.5), gated on small lymphocytes and analyzed on a FACScan (TM) flow cytometer (BDIS, San Jose, CA). Amount used: 1 ug/10e6 cells