Analysis of lymphoid cells and their subpopulations in the blood. Cell suspensions isolated from the blood of control GF piglets and GF piglets infected with PRRSV, SIV or PCV2 (different animal groups depicted on x-axes) were analyzed by flow cytometry for the proportion of some B cell subpopulations (A-C), αβ T cell subpopulations (D-F) and γδ T cell subpopulations (G-I). The phenotype of individual cell subpopulations is depicted above each graph. Note that the proportion of total B, αβ T, γδ T and NK cells did not differ between experimental groups and therefore these are not shown. The same applies for CD2—CD21+ B cell subpopulation. Bars represent mean values obtained during monitoring of animals at dpi 0 (open bars), 7 (light-grey bars), 14 (dark-grey bars), 21 (light-black bars) and 28 (black bars). Error bars represent ± standard deviation. Values that show statistically significant difference (p < 0.05) from day 0 values are indicated by asterisk. Statistical analyses were done using paired t-test so that levels of significance reflect behavior of all pigs in a given group.