Few babies born to HIV-infected mothers carry the disease in utero, , even though HIV is a blood-borne virus and there is a constant flow of blood through the umbilical cord that could infect the growing fetus. As genetic testing has demonstrated, this is because the human fetal immune system may develop separately from the adult immune system, and it may provide a measure of protection. When exposed to foreign cells, immune cells “activate” to become T-cells, which defend the organism. Fetal T-cells seem to be more tolerant of HIV and do not cause the reactions typically seen in HIV infection; these cells recognize the foreign cells but do not fight them, and the virus is not stimulated to destroy the T-cells, as happens when an individual has full-blown AIDS.

1. Which sentence provides the best summary of the passage?

A. Foreign cells cannot enter fetuses’ bloodstreams as easily as they can enter the bloodstreams of adults.
B. The reason few fetuses contract HIV from infected mothers is that their mothers’ T-cells protect them.
C. The fetal immune system may not be similar to the adult immune system.
D. T-cells affected by HIV are not activated in the fetal immune response and therefore remain more tolerant of foreign cells.
E. Fetuses rarely contract HIV in utero because the fetal immune system operates differently than the adult system.


2. Which of the following statements are suggested by the passage?

I. Fetuses are better protected from HIV than their mothers because of their respective immune systems.
II. If researchers could find a way to stop T-cells in adults from activating, adults would have the same health benefit as fetuses.
III. Fetal immune systems are more complicated than those of adults.