By comparing the basal TNF-α production by non-stimulated BALF leukocytes from all breeds, it was found that Hampshire cells produced significantly more TNF-α than the Large White cells at pre- and post-infection and likewise the cells from Pietrain also produced significantly increased levels as compared to those from Large White pigs at 4 days post-infection (Fig. 1C and Additional file 1). Here, TNF is linked to infection.