Which type of immunity is acquired through vaccination or exposure to a specific pathogen?

Explanation: T cells are a type of lymphocyte that plays a central role in cell-mediated immunity. They can recognize and destroy abnormal cells, including cancer cells, through direct cell-to-cell interactions.

Incorrect choices:

b. B cells produce antibodies in response to specific pathogens, but they do not directly attack cancer cells.

c. Antibodies are protein molecules that can bind to specific antigens on pathogens, but they do not have a direct role in attacking cancer cells.

d. Macrophages are phagocytic cells that engulf and destroy foreign substances, including pathogens, but they are not the primary cells responsible for recognizing and attacking cancer cells.

Explanation: Passive immunity is acquired when preformed antibodies are transferred to an individual, providing immediate but temporary protection against a specific pathogen. This can occur naturally from a mother to her newborn or artificially through administration of specific antibodies.

Incorrect choices:

a. Active immunity is acquired when the body's immune system is exposed to a pathogen and produces an immune response to provide protection against future infections.

c. Natural immunity refers to immunity that is acquired through natural exposure to a pathogen, either through infection or vaccination.

d. Herd immunity is the indirect protection that occurs when a large percentage of a population becomes immune to a disease, either through vaccination or previous infection, reducing the likelihood of transmission to susceptible individuals.