Maternal IgG

Enterocytes Maternal IgG, dimeric IgA, transcobalamine-Bi2/ intrinsic factor... 

In areas where malaria is hyper- or holoendemic, newborn infants had high titers of malarial antibody which decreased during the first 6 months of life and then showed a gradual rise throughout childhood until adult levels were attained. The pattern of the malarial fluorescent antibody titer in children in a malaria endemic area, reflected the development of the serum IgG more closely than that of any other immunoglobulins, and the early fall in the titer of the malaria fluorescent antibody coincided with that of the loss of maternal IgG from the children s circulation, implying that malarial antibody is quite capable of traversing the human placenta (M13) (Table 6, Fig. 6). 

The neonate lacks the ability to mount a full immunological response, accordingly maternal IgG is transported across the placenta late in pregnancy and is also absorbed across the gastrointestinal tract from breast milk. Maternal IgA secreted into breast milk will also provide mucosal protection for the neonate. 

Both ligand and receptor transportation out of the cell (e.g., maternal IgG, secretory IgA Chapter 35). 

IgG, the most prevalent of the antibody classes, comprises approximately 80% of serum antibody. IgG is usually the second isotype of antibody to be produced in an initial humoral immune response. IgG is the only isotype of antibody that can cross the placenta. Therefore, early maternal humoral protection of neonates is primarily due to maternal IgG that crossed the placenta in utero. 

A FIGURE 17-34 Transcytosis of maternal IgG immunoglobulins across the intestinal epithelial cells of newborn mice. This transcellular movement of a ligand involves both endocytosis and exocytosis. The one-way movement of ligand from the intestinal lumen to the blood depends on the differential affinity of the Fc receptor for antibody at pH 6 (strong binding) and at pH 7 (weak binding). Transcytosis in the opposite direction returns the empty Fc receptor to the luminal membrane. See text for discussion. 

Figure 9.2-4 Schematic representation of the ratio of fetal/maternal IgG concentrations throughout gestation in the macaque and relationship of the fetal antibody exposure relative to the period of organogenesis. Serum IgG concentrations shown in the graph have been adapted from data from Coe et al. (1993, 1994) and Fujimoto et al. (1983).

Figure 5.34 Movement of maternal IgG across the intestinal epithelium of newborn mice. Adapted from [13, 14].

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