FIG. 4.

Proliferative responses to 10⁸ CFU of gamma-irradiated SRB51 by PBMC after booster vaccination of elk with saline, S19, or SRB51. Elk were initially vaccinated with saline, 1.2 × 10¹⁰ CFU of SRB51, or 0.8 × 10¹⁰ CFU of S19 (n = seven animals/treatment) and booster vaccinated 65 weeks later with saline, 1.0 × 10¹⁰ CFU SRB51, or 1.2 × 10¹⁰ CFU S19, respectively. Cells were incubated at 37°C and 5% CO₂ for 7 days and then pulsed for 18 h with [³H]thymidine. The results are expressed as mean stimulation indexes. Means within a sampling time with different superscripts are significantly different (P < 0.05). The mean response of elk PBMC incubated in the absence of antigen was 2,278 ± 300 cpm. The mean response of elk PBMC incubated with 1 μg of pokeweed mitogen/ml was 70,626 ± 4,553 cpm.