Maternal antibodies and immune responsiveness in growing lambs
M.R. McQuoid, A.J. Hodgkinson, S.C. Hodgkinson
AgResearch, Ruakura Agricultural Centre, Private Bag 3123,
Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1995,
55: 214-217
In ruminants protection against environmental pathogens in the early
post-natal period is largely dependent on passively-acquired immunity from
maternal colostrum since evidence suggests placental transfer of antibody
does not occur. Our overall aim is to develop antibody based treatments for
protection of neonatal animals. In this study we have re-examined aspects of
maternal antibody transfer to offspring especially in the light of recent
evidence that feeding specific antibodies to neonatal rats decreases
subsequent immune responses to the corresponding antigen. In experiment
1, pregnant ewes immunised with model antigen (human growth hormone)
were terminated at 135 days gestation and blood samples collected from the
ewe and fetus. Analysis of fetal plasma by antibody dilution/tracer binding
assay procedures produced no evidence of antibody transfer to the fetal
circulation via the placenta. In a further study the kinetics of specific
antibodies were examined in lambs from immunised ewes. One group of
lambs was permitted to suckle from the ewe for the duration of the trial (40
days) whereas the other group was permitted initial sucklings only, separated
from the ewe 24 hours post partum and then fed a milk substitute. Analysis
of specific antibodies titres revealed a very similar trend in both the amount
of antibody transferred to lamb plasma and its persistence with the half-life
for both groups calculated at approx. 13 days In the second experiment
lambs from ewes immunised during pregnancy against E.coli and fed
specific antibodies via maternal colostrum as neonates were compared to a
matched control group of lambs derived from non-immunised ewes for
subsequent immune responses against the same antigen. Peak antibody titres
as analysed by ELISA were lower in lambs from immunised ewes than in
control group lambs (mean titre (-log 10) 5.29 ± 0.19 and 5.57 ± 0.10
respectively) although the difference was not significant (p<0.39, unpaired
T-test). As a consequence we have found using lambs little evidence to
support previous findings in rats that feeding specific antibody to neonatal
animals serves to suppress subsequent immune responses to the
corresponding antigen.
Keywords: NZSAPAB;
antibodies; immune response; hyporesponsiveness; lamb; sheep
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Last Updated 25-01-1997
