Primary genital C. suis infection of the re-infection group (nine-week-old pigs) resulted in increased secretion of TNF-α, IL-1β, IL-6 and IL-12p40 by PBMC, whereas primo-infection of the infection group (seventeen-week-old animals) decreased the IL-1β, IL-8 and IL-10 secretion by PBMC. This evidence concerns the gene IL6 and infection.