Match the following choices to the statements in questions 5–7:
a. IgA
b. IgD
c. IgE
d. IgG
e. IgM


Antibodies that protect the fetus and newborn.

Verified step by step guidance

1. Identify the function of each antibody type: IgA, IgD, IgE, IgG, and IgM.
2. Understand that IgG is the only antibody that can cross the placenta to provide passive immunity to the fetus.
3. Recognize that IgA is primarily found in mucosal areas and secretions like saliva and breast milk.
4. Note that IgM is the first antibody produced in response to an infection but does not cross the placenta.
5. Conclude that IgG is the antibody that protects the fetus and newborn by crossing the placenta.

Key Concepts

Antibody Classes

Antibodies, or immunoglobulins, are proteins produced by B cells that play a crucial role in the immune response. There are five main classes of antibodies: IgA, IgD, IgE, IgG, and IgM, each with distinct functions and locations in the body. Understanding these classes is essential for identifying their specific roles in immune protection.

IgG Function

IgG is the most abundant antibody in the bloodstream and is known for its ability to cross the placenta, providing passive immunity to the fetus. It plays a vital role in long-term immunity and is crucial for neutralizing pathogens and opsonizing bacteria for phagocytosis. This characteristic makes IgG particularly important for protecting newborns.

Passive Immunity

Passive immunity refers to the temporary immunity gained through the transfer of antibodies from one individual to another, such as from mother to fetus via the placenta or through breast milk. This type of immunity is crucial for newborns, as their immune systems are not fully developed at birth, and it provides immediate protection against infections during the early stages of life.