T-cell–independent antibody responses. (A) BRGS and hBAFFKI-BRGS hu-mice were immunized with NP-Ficoll and antibody responses to NP were measured in serially diluted serum by ELISA. Human serum was used as negative control (top graphs). NP-specific IgM and IgG responses are indicated as O.D. (405 nm) values. Top graphs are representative ELISA curves after the subtraction of background signal. Data from 3 independent experiments were combined in the bottom graphs. Each experiment (set) showed similar differences between mBAFF and hBAFF samples. The graph reports O.D. values corresponding to the same serum dilution for every sample within a set of ELISAs and within the linear part of the ELISA curves. The serum dilution in each of the 3 sets was selected based on the condition that the average O.D. of the mBAFF group was similar between sets. (B) Bottom graphs display anti-NP IgM and IgG O.D. (405 nm) values for a subset of hu-mice with similar total IgM and IgG levels (top graphs). *P < .05; **P < .01.