Figure 5.

Disruption of RA signaling in CD8⁺ T cells impairs clonal expansion and function in vivo in response to OVA, α-CD40, and pl: C immunization. dnRARα and dnRARαCD4^Cre mice were immunized as described in Material and Methods on day 0. A–C, reduced clonal expansion. Representative analysis of tetramer staining (A), kinetics in the blood (B), and distribution of OVA tetramer⁺ cells in blood, spleen, PLN, and MLN (day 6; C) are shown. In all the examined organs, shown is the CD44^hiOVA tetramer⁺ percentage in CD8⁺MHCII⁻ T cells. Data shown in A and B are representative of 4 experiments (n ≥ 3 mice per group in each experiment). Statistically significant differences were determined by 2-way ANOVA analysis of pooled experiments (n ≥ 12 mice per group) in B. Data shown in C are pooled from 2 experiments (n = 7 mice per group). Statistically significant differences were determined by t test. D and E, reduced IFN-γ recall responses. Blood samples from immunized mice as in A–C (day 6 postimmunization) were incubated in the presence of brefeldin A with or without SIINFEKL peptide or α-CD3 for 18 hours at 37°C. Cytoplasmic IFN-γ staining was determined (D) and quantified (E) and reported as the CD44⁺IFN-γ⁺ percentage in CD8⁺ T cells after restimulation. Statistically significant differences were determined by t test. Data shown are representative of 4 experiments with similar results (n ≥ 3 mice per group in each experiment).