FIG. 4.

Anti-4-1BB-mediated inhibition of the primary anti-PspA response and the generation of PspA memory decreases steadily with a delay of injection of MAb up to day 8. Separate groups of mice (five each) were immunized with R36A. Anti-4-1BB MAb was injected into different groups of mice on different days after R36A immunization as indicated. Mice were boosted with R36A 6 weeks after primary immunization and boosted again 2 weeks later. Sera were obtained on day 14 (primary anti-PspA) and at 8 weeks (secondary anti-PspA) and 10 weeks (tertiary anti-PspA) for the determination of titers of IgG anti-PspA by ELISA. Data are representative of two similar experiments. ∗, P ≤ 0.05 relative to that for mice treated with rat IgG (broken lines).