Activation of T cells in the tLN. Incremental loss of CFSE intensity by KJ1.26⁺CD4⁺ cells 72 hours after heat-aggregated ovalbumin (HAO) challenge in the ear showed proliferation of adoptively transferred DO11.10 T cells in BALB/c mice with established tLNs. Representative flow cytometric plots of PBS-challenged cervical LN (A) and tLN (B). An expanded KJ1.26⁺CD4⁺ population is seen in both cervical (C) and tLN (D) after antigenic challenge. Incremental loss of CFSE intensity of KJ1.26⁺CD4⁺ cells in the cervical LN and tLN (E-F), reflecting Ag-specific proliferation that is summarized graphically (G). Data represent the mean of triplicate samples ± SD (n = 2).