The humoral immune response in Atlantic salmon ( Salmo salar L.) against the hapten carrier antigen NIP-LPH; the effect of determinant (NIP) density and the isotype profile of anti-NIP antibodies

Abstract

The humoral immune response in Atlantic salmon ( Salmo salar L) against the semi-synthetic antigen NIP-LPH (4-hydroxy-3-iodo-5-nitrophenyl-acetic acid conjugated to Limulus polyphemus haemocyanin) was studied. The effect of the conjugation ratio on the antibody activity, affinity, specificity and shift of isotypic determinants of anti-NIP antibodies was tested. No affinity maturation of the antibody response similar to mammalian responses could be seen, except for the antigen having the lowest conjugation ratio (NIP 6 LPH) which demonstrated a moderate (two-fold) increase, of the average intrinsic association constant ( K 0 ) value from day 59–134 after immunisation. The NIP 6 LPH antigen also elicited anti-NIP antibodies having a 15-fold higher K 0 than the more substituted NIP 19 LPH or NIP 37 LPH. By using a panel of monoclonal antibodies binding determinants on salmon Igs, a different spectrum of such determinants could be recorded on anti-NIP molecules in normal and immune salmon sera. Although the specificity of these monoclonal is unproven (i.e. react with the C or V regions on salmon Ig) these data suggest that Atlantic salmon have more than one antibody isotype and possess the ability to alter the composition of antibody classes during an ongoing immune response, akin to higher vertebrates.