Serum immunoglobulins and in vivo humoral responses. (A) IgM and subclasses of IgG immunoglobulins (Ig) were quantified in the serum collected from ADA^–/– mice that received GT (^–/– GT; n = 6) or BMT (^–/– BMT; n = 6), 17 weeks after treatment. Serum Ig from untreated age-matched ADA^+/+ mice (n = 7), 18-day-old ADA^–/– mice (n = 13), or ADA^+/+ mice (n = 4) are shown as controls. Each dot represents values obtained in a single mouse. Serum IgM, IgG1, and IgG3 were normal in ADA^–/– GT and ADA^–/– BMT mice, while IgG2a levels were not different between GT and BMT. (B) Ova-specific Ig production. ADA^–/– mice treated with GT (n = 2) or BMT (n = 2) and age-matched ADA^+/+ mice were challenged with Ova or adjuvant only. Ova-specific Ig belonging to different classes were measured weekly in the serum for 1 month.