Characterisation of porcine blood monocytes (Mo) and monocyte-derived macrophages (MDM) by flow cytometry following staining with anti-SWC1 (A) and anti-SWC9 (B) mAb. In (A) and (B), the filled-histograms represent the Mo collected on day 0, and the opened histograms represent the MDM after 3 days of incubation with 30% of pooled PCV1-, PCV2-, and PRRSV-free porcine plasma. The data of the positive rates of SWC1 and SWC9 (C) as well as MHC I and MHC II (D) are expressed as percentages and shown as mean ± SD of 6 pigs from three independent experiments in triplicate. *The difference between Mo and MDM is statistically significant (p < 0.05). (C) ■: SWC1, □: SWC9; (D) ■: MHC I, □: MHC II.