Figure 4.

Activated ICOS^−/− CD4 T cells express higher concentrations of the lymph node homing molecules CCR7 and CD62L than do wild-type CD4 T cells. DO11.10 and ICOS^−/− DO11.10 cells were assessed on Day 4 after adoptive transfer, as described in Figure 2. (A) CD4⁺KJ1–26⁺ cells were evaluated for the expression of CD62L, shown as a representative plot (left, wild-type, gray shaded histogram; ICOS^−/−, black line), the total percent of CD62L^high cells (middle), and the percent of cells in each cell division expressing CD62L (right). (B) The expression of CCR7 was analyzed in CD4⁺KJ1–26⁺ cells. A representative plot is shown (left, wild-type, gray shaded histogram; ICOS^−/−: black line). The median fluoresence intensity (MFI) of CCR7 of all CD4⁺KJ1–26⁺ cells (middle) and the MFI of CCR7 in each cell division (right) were measured. Experimental results in A and B were replicated in two independent experiments (n ≥ 4 for each experiment). (C) OTII and ICOS^−/− OTII cells were labeled with CFSE and adoptively transferred to ICOSL^−/− or WT congenic hosts, which were immunized with inactivated S. mansonii eggs and ovalbumin_323–339 peptide (OVAp). On Day 4, the CD62L expression of T cell receptor-transgenic cells at each cell division was quantified. Representative plots show the CD62L^high and CD62L^low fractions of each generation for each condition. The percent CD62L^high within a generation is calculated as CD62L^high/total in generation (i.e., CD62L^high/[CD62L^high + CD62L^low]). For A and B, significance was determined by unpaired Student's t tests. For C, significance was calculated by 2-way ANOVA. For all results, *P < 0.05, **P < 0.01, and ***P < 0.001.