Question

For the first several months after birth, a newborn didn't experience any problems with sickness. After that, however, he had many severe bacterial infections. The most likely reason for the delayed onset of this problem was:

A. It took several months for the thymus to develop fully
B. For the first several months he had passive natural immunity from antibodies passed to him through the placenta
C. He had active artificial immunity during the first several months
D. He had degeneration of his normal immune function after birth

Answer 1

The most likely reason is passive natural immunity from antibodies passed through the placenta.

Step-by-step explanation:

The most likely reason for the delayed onset of severe bacterial infections in the newborn is B. For the first several months he had passive natural immunity from antibodies passed to him through the placenta. Passive immunity is acquired naturally by the fetus through the mother's blood. Antibodies are transported from mother to fetus across the placenta, so babies have high levels of antibodies at birth, providing them with protection from common pathogens until their own immune system matures.