T cell-dependent PC survival in tonsil grafts. To assess the role of T cells in PC survival in the grafts, xenochimeric mice were treated with either anti-CD3 (OKT3) or anti-CD154 mAbs. Levels of hIgG and mIgG assessed by ELISA and recovered graft composition assessed by immunofluorescence were analyzed. (A) Mean levels of hIgG (ng/mL) in untreated (Con), OKT3-treated (OKT3), or anti-CD154–treated (CD154) mice. Error bars represent SEM for treatment groups. (B) Mean levels of mIgG (ng/mL) in mice treated with OKT3 or anti-CD154 mAbs. Error bars represent SEM for treatment groups. (C) Tonsil graft sections from control and OKT3-treated and anti-CD154–treated mice stained for expression of human CD138 (green), CD3 (red), and CD45 (blue). Scale bar represents 50 μm. Results are representative of 3 experiments.