Question

Which antibody can cross the placenta?
(a) IgE
(b) IgA
(c) IgG
(d) IgM

Answer 1

Hint: Most abundant isotype within the plasma, and comprises 80 percent of the entire antibody content within the serum. It detoxifies matters that are harmful and allow the antibody-antigen complex.

Complete step by step answer:
IgG is transferred to the placenta by the fetus and saves the infant until its birth. IgG is split into four subclasses- IgG1, IgG2, IgG3, and IgG4. Among these, only IgG3 and IgG4 possess the power to cross the placenta. The heavy chains of IgG have two antigen- binding areas and are of the subclass gamma. It facilitates the method of phagocytosis and provides immunity to the developing fetus. It neutralizes the toxins and pathogens and offers protection to the body.
- IgM is the primary antibody induced in response to a microbial attack by B cells. It is the most important antibody and is found during a pentameric form. It circulates within the blood and lymph and constitutes 6 percent of the entire antibody content within the serum. It’s involved in agglutination and opsonization. It is an outsized number of antigenic sites on its surface and thus facilitates efficient activation of the system. - Usually, IgA is found in liquids like breast milk, serum, saliva, fluids of the intestine. IgA in breast milk protects an infant’s alimentary canal from microbial activity. It constitutes 13 percent of the entire antibody content within the serum. It provides the primary line of defense against the pathogens and limits inflammation. It also activates the complement pathway and participates within the immune reaction. - IgE is present within the least amounts, around 0.02 percent of the antibody content within the serum. These are present within the linings of the respiratory and intestinal tracts and answer allergies. 
So, the right answer is ‘IgG’.

Note: Antibody (Ab)  is additionally referred to as an immunoglobulin (Ig) . These are large, Y- structure blood proteins manufactured by plasma cells. They bind to foreign particles and invade them. These particles are foreign bodies that get bombarded by antibodies. Few antibodies bind the antigen present on the pathogens. These aggregate the pathogen and they remain in secretions. When the secretion is expelled out, the antigen is additionally expelled.