Figure 4.

Adoptive transfer of Tregs into mice infected with a low dose of IAV resulted in severe disease symptoms. (A) Scheme of adoptive transfer study. Nine mice were infected with the low dose of IAV (3 x 10³ pfu) (purple, orange, and grey arrow). In parallel, 10 donor mice were infected with the high dose (3 x 10⁵ pfu) of IAV (red arrow). On day 4 p.i., these mice were sacrificed, and Tregs were isolated from the spleen. 1 x 10⁶ cells each of this Treg fraction were administered intravenously to all infected mice of group 2 (purple) (n = 3). In parallel, rapamycin was administered intraperitoneally to all infected mice of group 3 (orange) (n = 3). This treatment was repeated on day 5 and day 6 p.i. Animals in group 4 (grey) served as infected, untreated controls (n = 3). Observation parameters included (B) change of body weight, (C) temperature as the mean of the day, and (D) disease symptom scores.