Partial inhibition of the humoral immune response of pigs after early postnatal immunization.

The ability of young pigs to be immunized during the postnatal period was studied. Eight groups of pigs born on the same day from 3 sows were injected with hen egg-white lysozyme in Freund's incomplete adjuvant at days 0, 1, 2, 3, 4, 5, 7, and 10 after birth. The serum antibody titers were determined each week. Results indicated that pigs injected within the first 3 days of life exhibited a delay of 10 days in the appearance of the humoral antibodies, compared with the antibody response observed in pigs injected later. Serum antibody titers were markedly lower in the early immunized pigs. The secondary immune response was similar in all pigs. This partial inhibition is not directly linked to the corticoids present in the serum at the immunization day. Possible reasons for this impairment of the humoral immune response were reviewed.