Variation in immune response in neonatal pigs
Variation in immune response (IR) has been described in many species. Immunophenotyping should be done as early a possible to facilitate related actions, such as selective breeding, hence a standard protocol was developed for test-immunizing neonatal piglets. In three outbred and five inbred litters, Yorkshire pigs were immunized simultaneously with hen egg white lysozyme (HEWL) and killed 'Candida albicans' (CA) in Quil-A adjuvant at 14 and 28 days of age. Antibody (Ab)-mediated IR (AMIR) was measured by enzyme-linked immunosorbent assay (ELISA) and AMIR and cell-mediated IR by intradermal (ID) injection of antigen and monitored by double skin-fold thickness (DSFT) measurement. Variation within and between litters was significant and was greater in IR to HEWL than to CA. Immunoglobulin (Ig)G1 and IgG 2-related Ab activity and DSFT after ID injection of HEWL and CA, confirmed that HEWL induces a type 2 IR and CA a complex type 1 IR. Apparent passive transfer of maternal IR bias to offspring was observed. Variability in IR was similar in inbred and outbred litters. Systemic injection of recombinant porcine interferon gamma increased blood mononuclear cell expression of major histocompatibility antigen and affected rate of gain but did not influence IR bias. Piglets may be immunophenotyped beginning at 14 days of age and HEWL and CA are valid antigens for this purpose.