What could have caused the weakly positive DAT in the infant born to an O-negative mother with a B-positive blood type?

What could have caused the weakly positive DAT in the infant born to an O-negative mother with a B-positive blood type?

• A. Anti-D from the mother coating the infant red cells
• B. An alloantibody, such as anti-K, coating the infant red cells
• C. Maternal anti-B coating the infant cells
• D. Maternal anti-A, B coating the infant cells

Answer: (D)

The weakly positive Direct Antiglobulin Test (DAT) in the infant can be attributed to the presence of maternal antibodies that cross the placenta and coat the infant's red blood cells. In this case, the infant, being type B-positive, has inherited B antigens. The mother, who is O-negative, does not have A or B antigens but can produce antibodies to both due to her blood type, which lacks these antigens. Maternal anti-A and anti-B antibodies can pass through the placenta during pregnancy and may attach to the corresponding antigens on the infant's red blood cells, resulting in a weak positive DAT. Since the infant has B antigens on their cells, the mother's anti-B antibody is particularly relevant in this situation. The presence of these antibodies is what leads to the weakly positive DAT result, indicating that there is an immune response involving the infant's red blood cells due to maternal antibodies. The other potential causes, while plausible in theoretical scenarios, do not fit as directly with the information provided. For example, anti-D from the mother would not be relevant, as the mother is O-negative and does not produce anti-D antibodies without prior sensitization, which is not mentioned in this scenario. Other alloantib

The weakly positive Direct Antiglobulin Test (DAT) in the infant can be attributed to the presence of maternal antibodies that cross the placenta and coat the infant's red blood cells. In this case, the infant, being type B-positive, has inherited B antigens. The mother, who is O-negative, does not have A or B antigens but can produce antibodies to both due to her blood type, which lacks these antigens.

Maternal anti-A and anti-B antibodies can pass through the placenta during pregnancy and may attach to the corresponding antigens on the infant's red blood cells, resulting in a weak positive DAT. Since the infant has B antigens on their cells, the mother's anti-B antibody is particularly relevant in this situation. The presence of these antibodies is what leads to the weakly positive DAT result, indicating that there is an immune response involving the infant's red blood cells due to maternal antibodies.

The other potential causes, while plausible in theoretical scenarios, do not fit as directly with the information provided. For example, anti-D from the mother would not be relevant, as the mother is O-negative and does not produce anti-D antibodies without prior sensitization, which is not mentioned in this scenario. Other alloantib