Immune responses of 129Ola × C57BL/6J F3 CD38^−/− mice (open symbols) and CD38^+/+littermate controls (closed symbols) to TI-2 antigens. Titers of λ-bearing 1→3 dextran-specific serum antibody (A), or λ-bearing NP-specific serum antibody (B) in individual mice at day 7 after immunization with 50 μg of 1→3 dextran, or 10 μg of NP₂₇-Ficoll, respectively. The 1→3 dextran data shown represent the composite results from four independent immunization experiments and include 17 CD38^−/− mice (mean = 1131.1 μg/mL) and 17 CD38^+/+ littermate controls (mean = 247.3 μg/mL). The NP₂₇-Ficoll data shown represent the composite results from three independent immunization experiments and include 15 CD38^−/− mice (mean = 172.4 μg/mL), and 13 CD38^+/+ littermate controls (mean = 233.9 μg/mL).