Cell-mediated immune response in pigs persistently infected with a Mycobacterium avium strain

Following a persistent bacterial infection with a Mycobacterium avium strain in pigs, the lymphocyte stimulation (LS), leucocyte migration inhibition (LMI) and tuberculin skin reactivity responses were studied. The responses in the LS and LMI tests occurred within a period of 35 to 49 days after infection. Positive tuberculin skin responses were found 40 to 70 days after infection. No direct correlation was evident between the LS and LMI tests during the experimental period. The responses to purified protein derivatives (PPD) in the LMI test were of shorter duration than those seen in the LS test. The course of LS in pigs expressed high, lower and non-stimulatory responses to the tested PPDs. At the end of the experimental period, 173 days after infection, lymphocyte stimulatory reactivity to PPDs could be demonstrated in all pigs, whereas a positive tuberculin skin test was observed in only one animal. Lymphocyte responses to M avium PPD were generally higher than were the other tested PPDs.