An organ that shrinks after puberty is the:

A. Blood contains various types of cells, such as red blood cells and white blood cells, but dust cells are not found in the blood.
B. Dust cells are a type of macrophage found in the lungs. They are responsible for engulfing and clearing inhaled particles, dust, and pathogens from the respiratory system.
C. The liver contains Kupffer cells, which are macrophages that filter blood, but dust cells are not found in the liver.
D. The small intestine contains various immune cells, but dust cells are not among them. The small intestine has its own specialized immune cells like Peyer's patches.

A. Neutrophils are a type of white blood cell that primarily responds to bacterial infections and perform phagocytosis, not specifically attacking tumor or virus-infected cells.
B. Regulatory T cells help regulate the immune response and prevent excessive immune activity, but they do not directly attack tumor or virus-infected cells.
C. Natural killer (NK) cells are a type of lymphocyte that plays a key role in the body's defense against tumor cells and virus-infected cells by directly attacking and destroying them.
D. Memory T cells are responsible for "remembering" a previous pathogen, enabling a quicker response upon future exposure, but they do not directly attack tumor or virus-infected cells.