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

Explanation: Multiple sclerosis (MS) is an autoimmune disorder in which the immune system attacks the myelin sheath, the protective covering of nerve fibers in the central nervous system, leading to communication problems between the brain and the rest of the body.

Incorrect choices:

a. Rheumatoid arthritis primarily affects the joints, not the central nervous system.

b. Sjögren's syndrome primarily affects the salivary and lacrimal glands, not the central nervous system.

d. Crohn's disease is an autoimmune disorder that affects the gastrointestinal tract, not the central nervous system.

Explanation: Memory cells recognize and respond rapidly to previously encountered pathogens. Memory cells are a type of immune cell that are formed after an initial infection or vaccination. They "remember" the specific pathogen and allow the immune system to mount a faster and stronger response upon subsequent exposures to the same pathogen, providing long-term immunity.

Incorrect choices:

a. Memory cells do not directly attack pathogens in the body. They serve as a form of immune "memory" to help the body respond more effectively to future infections.

b. Memory cells do not produce antibodies upon initial pathogen exposure. B cells are responsible for producing antibodies in response to the pathogen.

d. Memory cells do not regulate the body's temperature during an infection. Temperature regulation is mainly controlled by the hypothalamus in the brain in response to infection or other stimuli.