The following antibodies were purchased from BD Biosciences: anti–mouse CD8-APC (Ly-2), anti–mouse CD44-FITC (Pgp-1, Ly-24), and B220-Cy (RA3–6B2). CD40 (1C10 or FGK45) were produced by hybridomas that were grown in serum-free conditions. Ova-specific CD8 T cells were detected by H-2Kb–specific tetramers containing the SIINFEKL peptide, either made as described previously (33 (link)) (a gift from Dr. Lefrancois, University of Connecticut Health Center, Farmington, CT) or purchased from Beckman Coulter.