Sorry to say that I think you should buy your instructor lunch. While
you are correct in the idea that the neonate would be protected
against most of the things the mother is immune to, there are other
considerations to think about.
First, consider the classes of antibodies. The neonate receives
primarily IgG from the mother, both in utero, and via milk. For this
reason, the neonate has no mucosal immunity, unlike the mother, who
develops mucosal immunity following mucosal exposure to
microorganisms. Even though the neonate may have plasma IgG, this
does not protect the mucous membranes.
Second, consider the antibody titers. Just because the neonate has
plasma Ab, this doesn't mean that the Abs are in sufficient amounts to
be protective. In addition, since the neonatal immune system is
underdeveloped, the neonate won't respond as vigorously to microbial
challenge as the mother would.
Third, an important facet of immunity is cell-mediated, which is not
transferred to the neonate. Rather, the neonate must develop this arm
of the immune response on his own. The lack of a well-developed CMI
response leaves the neonate at risk for both viral and fungal
infections. For this reason, oral Candida infections are very common
in the first 3 - 6 months of life.
Jay Mone'
