Intact T-cell–independent immune responses in B7-H2^–/– mice. Wild-type (•) and mutant (○) mice were immunized with (A) NP-LPS for the T-cell–independent type I and (B) NP-Ficoll for the T-cell–independent type II immune responses. Sera were collected one week after immunization, and the presence of NP-specific antibodies was quantified via ELISA. The value for each mouse was plotted, and the dilution of the immune sera is indicated. Preimmune sera were negative for the antigen-specific antibodies and were not shown. Statistical signifi-cance was determined using a paired 2-tailed Student t test, and the P values are indicated. Horizontal bars indicate the mean.