Which statement concerning anti-I is correct?

Which statement concerning anti-I is correct?

• A. it is a complement binding antibody
• B. it reacts best with cord red blood cells
• C. it does not bind complement
• D. it is only IgM

Answer: (A)

Anti-I is a cold agglutinin that targets the I antigen on adult red cells and is typically an IgM antibody that readily fixes complement at low temperatures. This complement binding leads to deposition of C3 on the red cells and can cause hemolysis or enhanced agglutination in testing. Cord red blood cells express little I antigen (they have more i antigen), so anti-I does not react well with them, explaining why it doesn’t react best with cord cells. The key point here is that anti-I can bind complement, which is why that statement is the best choice.

Anti-I is a cold agglutinin that targets the I antigen on adult red cells and is typically an IgM antibody that readily fixes complement at low temperatures. This complement binding leads to deposition of C3 on the red cells and can cause hemolysis or enhanced agglutination in testing. Cord red blood cells express little I antigen (they have more i antigen), so anti-I does not react well with them, explaining why it doesn’t react best with cord cells. The key point here is that anti-I can bind complement, which is why that statement is the best choice.