Fig. 5

T cells, B cells and germinal centre cell response. Immunized mice were challenge-infected and sacrificed 4 weeks post-challenge as scheduled. CD4⁺ T cells (a *P < 0.05) and CD8⁺ T cells (b *P < 0.05) populations in the spleen were determined. Mature B cells and germinal centre population were determined in the spleen (c, d *P < 0.05). Data are expressed as mean ± SD