Increased division of antigen-specific CD4⁺ T cells in the presence of poly (I:C), following transfusion with mHEL RBCs. After adoptive transfer of CFSE-labeled antigen-specific 3A9 × B6.PL-Thy1.1 CD4⁺ T cells, recipients were transfused with mHEL or control C57BL/6 RBCs, in the presence or absence of inflammation with poly (I:C). Three days later, splenocytes were analyzed for division of 3A9 × B6.PL-Thy1.1 cells. (A) Gating on Thy1.1⁺ adoptively transferred 3A9 × B6.PL-Thy1.1 cells. Numbers represent percentage of cells in gate. (B) CFSE division of the antigen-specific CD4⁺ T-cell population (gray shaded histogram is C57BL/6 control; dotted-line histogram is transfused with mHEL; and solid-line histogram is transfused with mHEL in the presence of poly (I:C)). Staining from representative mice is shown, and y-axes of histograms represent percentage of maximum peak value. This experiment was performed 3 times with similar results.