[Development of delayed-type hypersensitivity to hog cholera]

Leukocyte migration inhibition test showed that pigs with classical swine fever develop delayed type hypersensitivity. The highest migration inhibition (65-85%) was observed in animals with the acute form, on day 3 after infection, or directly before death, or in animals immunized with reactogenic strain with clinical signs of disease. In some pigs with acute form the migrating capacity of leukocytes was restored on days 7-8 postinfection. Leukocyte migration inhibition factor is detected in the sera of pigs starting from day 3 after infection with the virulent strain. The degree of delayed type hypersensitivity correlated with the outcome of classical swine fever.