Effect of Carrier Preimmunization on the Anti‐Hapten Response in the Chicken

Abstract

We found that chickens responded to an injection of 1 mg of alum‐precipitated conjugates of (4‐hydroxy‐3‐iodo‐5‐nitrophenyl)acetyl and bovine serum albumin (NIP‐BSA) or human gammaglobulin (NIP‐HGG) with an anti‐NIP response. This response was enhanced to fivefold titers if the birds were given a small dose (2 or 0.2 μg) of the carrier protein in complete Freund's adjuvant a week before injection. If the dose of the carrier was large (200–2,000 μg), it decreased the subsequent anti‐NIP response to the conjugate. The effect of the preimmunization correlated with the formation of anti‐carrier antibodies: a good anti‐carrier response was connected with inhibition and a poor anti‐carrier response with enhancement of the anti‐NIP response. Large preimmunization doses of the carrier caused enhanced anti‐hapten responses if the carrier was methylated or dodecanoylated; in this case the anti‐carrier humoral responses were weak. Large doses of the native carrier increased the subsequent anti‐hapten response if spleen cells of the preimmunized donors were injected into cyclophosphamide‐treated donors, who were then immunized with the hapten conjugate. The results confirm earlier studies indicating that collaboration of carrier‐specific cells and hapten‐specific cells is required in the chicken for an optimal anti‐hapten response. They further indicate that carrier‐primed cells do not reside in the thymus and that, also in birds, immunization by methylated or dodecanoylated protein causes good priming for helper function but bad priming for the antibody formation against the protein.