Abstract
Maternal immunity is the main early defense against infectious agents in newborns. Immunoglobulin G (IgG) is indispensable for immune defense against infectious agents. IgG is transported through either the colostrum or the placenta. Immunoglobulins are antibodies, and the five different classes of these antibodies are IgG, IgA, IgM, IgD and IgE. Through their biological function of binding antigens, antibodies facilitate the removal of antigens from the body. The placenta is a temporary maternal-fetal organ, whose principal function is to allow the controlled exchange of metabolites between mother and embryo/fetus during gestation. The placenta types in different species are classified by the number of membranes separating the maternal and fetal blood circulation. Humans, lagomorphs and rodents have hemochorial placentas, which require a receptor for IgG transfer. In other animals, such as horse and pig (epitheliochorial placenta), ruminants (synepitheliochorial placenta) and carnivores (endotheliochorial placenta), antibodies are transferred via the colostrum and absorbed by passive diffusion. This review covers immunoglobulin transport in several types of placentas.
Highlights
Maternal acquired immunity is the main early defense against infectious diseases in newborns [1]
We conclude from this review that Immunoglobulin G (IgG) is the only immunoglobulin class that can be transferred to the fetus during gestation
Only the hemochorial placenta is capable of transporting immunoglobulins during gestation
Summary
Maternal acquired immunity is the main early defense against infectious diseases in newborns [1]. To defend itself from the many existing pathogens, such as bacteria, viruses and other disease-causing agents, the body creates immunoglobulins, which recognize the antigens of B cells. These proteins are produced by the B cells themselves and have highly specific antigen recognition. IgG is responsible for neutralizing viruses and bacterial toxins, facilitating phagocytosis and lysing bacteria [13] During gestation, this immunoglobulin passes through the placenta from mother to fetus [15] [16]. The placenta can be classified by the number of membranes (layers of tissue of both maternal and fetal origin) that separate the maternal and fetal circulatory systems in the placental barrier region This yields four types of placentas: epitheliochorial, synepitheliochorial, endotheliochorial and hemochorial [17]. In other animals, including horses and pigs (epitheliochorial placenta), ruminants (synepitheliochorial) and carnivores (endotheliochorial), antibodies are transported through the colostrum [20]-[22]
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