Immunophenotype and lymphocyte function at 60 days after neonatal BMT. (A-D) The mice were age-matched (60 days) in the experimental arms: (1) Ada^+/+ (n = 4), (2) Ada^−/− BMT (n = 6), and (3) Ada^−/− ERT (n = 7). Data from the Ada^−/− with no treatment (at day 16) from Figure 1 are reproduced here as a historical control. *Significantly higher than untreated ADA-deficient mice (P < .001). **Significantly higher than untreated ADA-deficient mice or those treated with neonatal BMT or ERT (P < .001). Data are means plus or minus SEM. (A) Absolute numbers of thymocytes and splenocytes. (B) Absolute numbers in each thymocyte subpopulation (CD4⁺, CD8⁺, double-positive (DP): CD4⁺, CD8⁺, double-negative (DN): CD4⁻, CD8⁻). (C) Absolute numbers in each splenocyte subpopulation (CD4⁺, CD8⁺, CD19⁺) were calculated by multiplying the total numbers of cells collected from the organ by the percentage of cells in each subpopulation. (D) Lymphocyte proliferative function to conA was assessed as described in Figure 1. (E) Lymphocyte proliferative function was assessed by stimulating splenocytes with LPS for 48 hours, pulsing with ³H-thymidine for 20 hours, and determining the stimulation index compared with cells not treated with LPS: (1) Ada^−/− BMT (n = 5), (2) Ada^−/− ERT (n = 2), (3) Ada^+/+ (n = 2). (F) IgM production in response to vaccination with Pneumovax 23 in vivo. Preimmune sera were collected before vaccination and compared with sera collected 8 days postvaccination. IgM production was assessed by ELISA. (1) Ada^−/− BMT (n = 5), (2) Ada^+/+ (n = 3).