Figure 4.

hFIX-specific immune tolerance induced by IM of AAV1 is not accompanied by upregulation of regulatory T cells. Ten- to 12-week-old mice with C57BL/6 backgrounds (n = 13) were given IM of AAV1–hFIX (1 × 10¹¹ vg). Lymphocytes were collected from the mice 3–4 months after AAV injection for antibody staining and flow cytometry analysis as described. Tolerance to hFIX in the mice was verified by examination of hFIX antigen and anti-hFIX antibody at the time of lymphocyte collection. Lymphocytes from naive mice with the same backgrounds and matched age (n = 13) were examined simultaneously. This figure depicts frequency (% of CD4⁺ cells) of CD4⁺CD25⁺ and CD4⁺CD25⁺FoxP3⁺ regulatory T cells in the spleen of AAV1-injected tolerant and naive (control) mice with C57BL/6 background. AAV, adeno-associated virus; AAV1, adeno-associated virus serotype one; FIX, coagulation factor IX; hFIX, human FIX; IM, intramuscular injection.