Experimental design and presentation of (OVA)_323-339 peptide after exposure to either PyV.OVA-II or HOD RBCs. Recipient mice were infected with wild-type polyoma virus (PyV.WT) or polyoma virus expressing a known T-cell epitope (ovalbumin (OVA)_323-339), PyV.OVA-II. Two weeks after infection, recipient mice were transfused with RBCs from control FVB donors (expressing no HEL epitope), mHEL donors (expressing HEL on RBCs), or HOD donors (expressing RBC-specific HEL fused to OVA). (A) Diagram of experimental design: Sera were collected prior to transfusion and at 7 and 14 days after transfusion. (B) Diagram of B- and T-cell epitopes expressed in PyV.WT and PyV.OVA-II, as well as in FVB RBCs, mHEL RBCs, and HOD RBCs. Presence of the (OVA)_323-339 epitope is indicated by the green line. (C) OT-II Thy1.1 splenocytes were adoptively transferred into C56BL/6 mice followed by infection with either PyV.WT (C left) or PyV.OVA-II (C right). At 8 days after infection, splenocytes were harvested and stained for CD4 and Thy1.1. (D) OT-II splenocytes were adoptively transferred into C56BL/6.PL-Thy1.1 mice followed 24 hours later by transfusion with either HOD RBCs or FVB RBCs. At 4 days after transfusion, splenocytes were harvested and stained for CD4 and Thy1.2. Groups included mice receiving OT-II cells alone (left), OT-II cells and HOD transfusion (right), or OT-II cells and FVB transfusion (bottom).