ADA activity and metabolic detoxification. (A) ADA activity was measured in total cells (Tot) from spleen and lymph node (LN), as well as purified T cells (T) and B cells (B) from spleen 6 months after GT (–/– GT) or BMT (–/– BMT). No ADA activity was detected in lymphoid tissues from untreated ADA^–/– mice (–/–). ADA activity was not significantly different among ADA^+/+, ADA^–/– GT, and ADA^–/– BMT mice, with the exception of B splenocytes, in which it was higher in GT-treated mice (P < .01). (B) ADA activity was determined in peripheral RBCs at different months after treatments (–/– GT, n = 6; –/– BMT, n = 6). As controls, age-matched untreated ADA^+/+ (+/+;n = 9), ADA^+/– (+/–;n = 3) and 18-day-old ADA^–/– mice (–/–;n = 9) are also shown. Values are given as means and SDs of the measurements in each mouse. (C) Measurement of dAXP toxic metabolites in RBCs of GT-treated (–/– GT; n = 6) and BMT-treated (–/– BMT; n = 5) mice at 2, 4, and 6 months after treatment. In the right side of panels B and C, control values of untreated ADA^+/+ (+/+;n = 9), ADA^+/– (+/–;n = 3) and 18-day-old ADA^–/– mice (–/–;n = 9) are shown.