How does the immune system distinguish between self and non-self?

Explanation: Sjögren's syndrome is an autoimmune disorder in which the immune system attacks and damages the salivary and lacrimal glands, resulting in dry eyes and dry mouth.

Incorrect choices:

a. Rheumatoid arthritis primarily affects the joints, causing inflammation and joint damage.

c. Crohn's disease is an autoimmune disorder that affects the gastrointestinal tract, leading to inflammation and ulcers.

d. Psoriasis is a chronic skin condition characterized by red, scaly patches on the skin, and it is not related to the salivary and lacrimal glands.

Explanation: Antigens are unique molecules or proteins present on the surface of cells, including pathogens. The immune system can recognize these antigens as "non-self" and mount an immune response to eliminate them while sparing the body's own cells, which display different antigens that are recognized as "self."

Incorrect choices:

b. Recognizing different blood types is relevant for blood transfusions but not a primary mechanism of distinguishing self from non-self by the immune system.

c. Monitoring hormone levels in the body is not directly related to the immune system's ability to distinguish between self and non-self.

d. Cytokines are signaling molecules released by immune cells to regulate the immune response but are not the primary means of distinguishing self from non-self.