FIGURE 5. Abrogation of CTLA4 expression on Tregs by CTLA4Ig treatment is due to decreased peripheral homeostasis.
(A) Decreased Treg frequency and CTLA4 expression in thymectomized mice treated with CTLA4Ig. BALB/c mice were thymectomized, treated with CTLA4Ig or IgG2a as in Fig. 3A, and splenic CD4 T cells harvested 3 days post-treatment (day 7). Graphs show percentage of FoxP3+ (left) and CTLA4+FoxP3+ CD4 T cells (right) among total CD4 T cells from thymectomized IgG2a- and CTLA4Ig-treated mice. Results are an average of 4 mice per group and are representative of 2 experiments. The proportion of Tregs in IgG2a- and CTLAIg-treated sham-thymectomized controls were indistinguishable from intact mice similarly treated (data not shown). (B) Long-term reduction of FoxP3+ frequencies and CTLA4 expression on FoxP3+ Tregs following CTLA4Ig treatment. BALB/c mice were treated with IgG2a or CTLA4Ig as in Fig. 3A and the proportions of FoxP3+ (left) and CTLA4+FoxP3+ CD4 T cells (right) of total CD4 T cells were determined 3–28 days post-treatment. Results are expressed as mean percentage ± SD from 4–5 mice per group.