Antibodies (agglutinins) of the A and B red cell antigens (agglutinogens)
A. Are present in fetal plasma.
B. Cause haemolysis of RBCs containing the A and B antigens when added to a suspension of red cells in saline.
C. Do not normally cross the placental barrier.
D. Have a molecular weight in excess of 500 000.
E. Are monovalent
The correct answer is:
(C) Do not normally cross the placental barrier.
Antibodies against A and B antigens (agglutinins) are typically not present in fetal plasma, do not usually cross the placenta, and are involved in reactions that can cause hemolysis if they interact with corresponding antigens on red blood cells. They also tend to have a molecular weight higher than 500,000 and are generally bivalent.