Which of the following vaccines is typically recommended for adolescents to protect against certain types of cancer?

Explanation: The immune response is a complex system of defense mechanisms that aim to protect the body from pathogens, such as bacteria, viruses, and other foreign substances. It involves the activation of various immune cells, production of antibodies, and other immune components to recognize and eliminate the invading pathogens.

Incorrect choices:

a. Directly attacking and killing infected cells is the role of cytotoxic T cells during cell-mediated immunity, but it is not the primary purpose of the overall immune response.

b. Antigens are foreign substances that trigger the immune response. They are not produced by the immune response itself but rather recognized by immune cells and antibodies.

c. The immune response is not involved in regulating the body's metabolism. Metabolism regulation is primarily controlled by other systems in the body, such as the endocrine system.

Explanation: B cells are specialized in producing antibodies against specific antigens. When B cells encounter a pathogen or foreign substance with a matching antigen, they become activated and differentiate into plasma cells. Plasma cells then secrete large amounts of antibodies, which can recognize and neutralize the pathogen.

Incorrect choices:

a. B cells do not directly attack and kill infected cells. That role is primarily performed by cytotoxic T cells during cell-mediated immunity.

c. Regulatory T cells (Tregs) are responsible for regulating the immune response to prevent excessive inflammation and maintain immune homeostasis.

d. B cells recognize antigens presented by antigen-presenting cells like macrophages, but their primary function is to produce antibodies, not to recognize antigens directly.