Antibody titer induced by P. vulgaris administered in tilapia. Six groups (5 fish/group) of fish were I.P. immunized with hemocyanin supplemented with P. vulgaris (PV), FCA, P. vulgaris + FCA (PV + FCA), β-glucan, P. vulgaris + β-glucan (PV + glucan) and PBS as a control, respectively. Data represent the mean + S.D. (n = 5). Statistical differences (p < 0.05) between groups are indicated by different letters over the bar.