Page 762 - Veterinary Immunology, 10th Edition

mask the epitopes on vaccine antigens, preventing their recognition
VetBooks.ir by the animal's B cells. This suggestion is compatible with the

selective inhibition of B cell responses, the lack of inhibition of T cell
responses, and the evidence that, at least in humans and mice, high

doses of antigen can overcome maternal immunity. Thus for a
given vaccine dose, an immune response can be elicited only when
maternal antibody titers fall below a critical threshold.
In the absence of maternal antibodies, the newborn animal is able

to make antibodies soon after birth. For example, if calves fail to
suckle and are therefore hypogammaglobulinemic, their
endogenous IgM is detectable in blood by 4 days but only reaches
functional levels by 8 days. Serum IgG and IgA reach functional

levels by 16 to 32 days. In calves that have suckled and thus possess
maternal antibodies, antibody synthesis does not commence until
about 4 weeks of age. Likewise, colostrum-deprived piglets respond
to pseudorabies virus by 2 days after birth, but if they have suckled,

antibody production does not begin until 5 to 6 weeks after birth.
Colostrum-deprived lambs synthesize IgG1 at 1 week and IgG2 by
3 to 4 weeks. In colostrum-fed lambs, however, IgG2 synthesis does
not occur until 5 to 6 weeks.

Passively acquired maternal antibodies not only protect
newborns before their immune system becomes fully functional but
also may shape the B cell repertoire of the offspring. Mouse pups
nursed by mothers producing antibodies to vesicular stomatitis

virus developed higher endogenous antibody titers of this
specificity as they matured. As a result, these pups developed
higher titers of protective antibody when infected as adults.
Passively acquired maternal antibodies have a very significant

influence on the way in which a newborn's immune system
develops.

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