Th-cell-dependent immune responses in mice that underwent thymus transplantation. Aα^-/-, RFX5^-/-, CIITA^-/-, or C57BL/6^nu/nu mice received e14 thymi (TTX) either without further treatment (A,C-D) or after irradiation/2′-deoxyguanosine treatment (B). (A-B) Ten weeks after transplantation, the mice were immunized with NP-CG and boosted 3 weeks later. Blood was taken 3 weeks after the boost and analyzed for NP-specific IgG1. ○ indicates control mice; •, mice that underwent thymus transplantation. (C-D) MCMV-specific immune responses. Groups of 5 C57BL/6, RFX5^-/-, and RFX5^-/- mice that underwent thymus transplantation were infected with MCMV 6 months after transplantation, and viral titers were determined in salivary glands 3 weeks after infection. (C) IgG serum titers of MCMV-specific antibodies in RFX5^-/-,Aα^-/-, and C57BL/6 mice that did not undergo transplantation and RFX5^-/- or Aα^-/- mice that underwent thymus transplantation (TTX). OD indicates optical density. (D) Clearance of MCMV in salivary glands and lungs. PFU indicates plaque forming units. ⋄ indicates C57BL/6 mice; ○, RFX5^-/- control mice; and •, RFX5^-/- mice that underwent thymus transplantation.