FIG. 4.
Anti-FIV lymphoproliferative responses of vaccinated cats at different time points. The stimulation index was calculated as the ratio of [3H]thymidine incorporated by PBMC in the presence of FIV antigen to that in the presence of mock antigen. Arrows indicate the times that vaccine boosters were administered to all cats. Only a value of ≥2 was considered indicative of FIV-specific lymphoproliferation (broken lines). The mean stimulation index ± standard error for 23 assays carried out in the unvaccinated control cats that did not become infected was 1.6 ± 0.3.