Red blood cells are the least likely to be impacted by chronic stress affecting the immune system, as they are not directly involved in the body's immune response but are responsible for carrying oxygen.
The question asks which type of cell in Arianna's body is least likely to be impacted by chronic stress affecting the immune system. Red blood cells (a) red blood cells) are primarily responsible for carrying oxygen to the body's tissues and are not directly involved in the immune response, thus they are least likely to be impacted by a malfunctioning immune system.
On the other hand, B lymphocytes, macrophages, and T lymphocytes are all integral components of the immune system that can be affected by chronic stress. B lymphocytes produce antibodies, macrophages are phagocytes that can also promote inflammation, and T lymphocytes are involved in killing infected cells and regulating immune responses.
Therefore, while chronic stress can impair certain aspects of the immune system leading to a reduced ability to fight off pathogens, red blood cells are not directly involved in the immune response and therefore are the least affected by immune system malfunction.