In the absence of NK-cell activation, allogeneic skin grafting induces strong alloreactive CD4⁺ T-cell responses associated with Th2 cell development and massive eosinophil recruitment. (A-C) B6 CD8^−/− mice, treated or not with anti-NK1.1 PK136 mAb, received a skin graft from allogeneic BALB/c mice. Eight days after grafting, draining lymph nodes were harvested. Lymph nodes from naive mice were taken as control. Purified CD4⁺ T cells were cultured (2 × 10⁵ cells/well) in the presence of irradiated allogeneic BALB/c splenocytes (1 × 10⁵ cells/well) for 72 hours. (A) CD4⁺ T-cell proliferation was evaluated by ³H-TdR incorporation. Background proliferation was less than 500 cpm. (B) IFN-γ and (C) IL-4 productions were measured by enzyme-linked immunosorbent assay in 72-hour culture supernatants. Data are mean plus or minus SEM of 5 mice per group. (D) B6 CD8^−/− mice, treated or not with anti-NK1.1, received a skin graft from syngeneic B6, semi-allogeneic CB6F1, or fully allogeneic BALB/c mice. At the day of graft rejection (days 10-12), transplanted skins were harvested. Skin histologic analyses were performed, and the percentage of eosinophils among total mononuclear infiltrating cells was evaluated (3-5 mice per group). Data are from one representative experiment of at least 2 performed. *P < .05. **P < .01. N.S. indicates not significant.