A person who has a frontal-lobe brain injury is likely to experience a deficit in which of the following?

A. T-helper cells (CD4+ cells) play a crucial role in initiating and coordinating the immune response. They stimulate the activation of B-cells to produce antibodies and help activate cytotoxic T-cells to target infected cells.

B. The first line of defense against infection is provided by physical barriers like the skin, mucous membranes, and innate immune responses, not by T-helper cells.

C. While T-helper cells can activate macrophages indirectly by releasing cytokines, their primary role is in helping to activate other immune cells like B-cells and cytotoxic T-cells, rather than directly activating macrophages.

D. T-helper cells are not directly involved in minimizing cell damage caused by T-cells. That role is more closely related to regulatory T-cells (Tregs) that help maintain immune tolerance and prevent excessive immune responses.

A. A vesicle is involved in the transport of substances within or out of the cell via processes like endocytosis or exocytosis but does not directly permit ion passage across the membrane.
B. An enzyme catalyzes chemical reactions and is not directly involved in the transport of ions across the cell membrane.
C. A channel protein facilitates the passage of ions across the cell membrane, allowing specific ions to move in and out of the cell based on concentration gradients.
D. A lysosome is an organelle responsible for digesting and breaking down waste materials within the cell, not for ion transport across the membrane.