FIG. 1.

CD1d expression and NKT cells are required for optimal production of PA-specific Abs. C57BL/6, CD1d^−/−, and Jα18^−/− mice were immunized s.c. with 10 μg of PA or 10 μg of PA plus 2 μg of α-GC in a 100-μl volume of sterile endotoxin-free PBS. Sera were collected before immunization and on day 28 (data not shown). On day 28 mice were then boosted with half the original dose of PA and sera collected again on day 38 (d38) (a) and day 43 (b). ELISAs were performed to determine the endpoint anti-PA IgG1 titer. Data points represent the endpoint titers for individual mice. (c) Since only two CD1d^−/− mice were used in the first experiment, additional groups of C57BL/6 and CD1d^−/− mice were immunized with PA and analyzed at day 43. (d) Responses in Jα18^−/− mice are shown in a third experiment (also day 43 bleeds). Geometric means are shown. Statistically significant differences between experimental groups are indicated by asterisks.