Tonsil graft PCs secrete high levels of human IgG. Secretion of hIgG by tonsillar PCs was assessed by ELISA and ELISPOT. (A) Weekly mean levels of hIgG (ng/mL) in the circulation of xenochimeric mice over 4-week grafting period in 6 independent experiments; each line represents data from a single experiment; error bars represent SEM. (B) Frequency of spots (hIgG) per 10 000 mononuclear cells recovered from tonsil (TN, □) or 10 000 live mononuclear cells recovered from TN grafts at 4 weeks after surgery (▩). Mean of 3 experiments shown, error bars represent SEM. (C) The mean spot size (1E-3 mm²) of cells secreting hIgG (□) and hIgM (▩) isolated from TN, TN grafts at 4 weeks after surgery, or bone marrow (BM). Mean of 3 experiments shown, error bars represent SEM.