Which statement is true regarding antibodies stimulated by transfusion or pregnancy and naturally occurring antibodies?

Which statement is true regarding antibodies stimulated by transfusion or pregnancy and naturally occurring antibodies?

• A. Immune antibodies from transfusion or pregnancy are usually IgG
• B. ABO antibodies are usually IgG
• C. Immune antibodies are usually IgM
• D. Antibodies stimulated by transfusion or pregnancy are usually IgG

Answer: (D)

The key idea is that antibodies formed in response to exposure to foreign red cell antigens, such as through transfusion or during pregnancy, are typically of the IgG class. IgG antibodies are small enough to circulate and, importantly, can cross the placenta, which is why alloantibodies formed after transfusion or pregnancy are usually clinically significant—they react with red cells at body temperature and can be detected by the antiglobulin test, leading to transfusion reactions or hemolytic disease of the newborn. Naturally occurring antibodies against ABO antigens are mainly IgM. They are present without prior exposure and tend to react at colder temperatures, which is why they’re generally less implicated in transfusion reactions at body temperature, though rare IgG anti-A,B can occur. So the statement that antibodies stimulated by transfusion or pregnancy are usually IgG correctly captures the typical class of clinically relevant alloantibodies, making it the best choice.

The key idea is that antibodies formed in response to exposure to foreign red cell antigens, such as through transfusion or during pregnancy, are typically of the IgG class. IgG antibodies are small enough to circulate and, importantly, can cross the placenta, which is why alloantibodies formed after transfusion or pregnancy are usually clinically significant—they react with red cells at body temperature and can be detected by the antiglobulin test, leading to transfusion reactions or hemolytic disease of the newborn.

Naturally occurring antibodies against ABO antigens are mainly IgM. They are present without prior exposure and tend to react at colder temperatures, which is why they’re generally less implicated in transfusion reactions at body temperature, though rare IgG anti-A,B can occur.

So the statement that antibodies stimulated by transfusion or pregnancy are usually IgG correctly captures the typical class of clinically relevant alloantibodies, making it the best choice.