Which type of immunity is acquired when an individual's immune system is exposed to a pathogen through vaccination or natural infection?

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.

Explanation: Active immunity. Active immunity is acquired when the immune system is exposed to a pathogen, either through natural infection or vaccination. It results in the production of memory cells that provide long-term protection against future exposures to the same pathogen.
Incorrect choices:

a. Passive immunity is acquired when preformed antibodies are transferred from one individual to another. It provides immediate but temporary protection and does not involve the production of memory cells.

b. Innate immunity is the body's first line of defense against infections and provides immediate, non-specific protection, but it does not involve the production of antibodies specific to a particular pathogen.

d. Acquired immunity is a general term that includes both active and passive immunity, but it does not specifically describe the type of immunity acquired through vaccination or exposure to a specific pathogen.