IMMUNOLOGY

Detailed explanation-1: -IgG is the only antibody class that significantly crosses the human placenta. This crossing is mediated by FcRn expressed on syncytiotrophoblast cells.

Detailed explanation-2: -Abstract. THE IgG of the neonatal human infant is almost entirely derived by selective transplacental passage of maternal IgG, but IgA and IgM are considered incapable of transplacental passage.

Detailed explanation-3: -The immunoglobulin, which cannot pass through placenta and such foetus is IgM.

Detailed explanation-4: -Although only IgG anti-A and anti-B can cross the placenta, these antibodies are found in the circulation of most newborn infants born to blood group O mothers.