Answer:
d. a second exposure to an allergen
Explanation:
An autoimmune disease is a condition that occurs when the immune system attacks and destroys healthy body tissues by mistake.
Normally, white blood cells (leukocytes), produced in the bone marrow and found in the blood, help to protect the body against invasive and harmful substances known as antigens. Examples are viruses, bacteria, toxins, cancer cells, etc. Leukocytes are a fundamental part of the immune system, whose main function is to produce antibodies that keep the human body protected from the action of these antigens by destroying them.
In the case of autoimmune diseases, the immune system cannot distinguish antigens from healthy body tissues and ends up attacking and destroying normal body cells.
The causes of autoimmune diseases are not yet known, although there are many mechanisms that trigger these diseases. However, we can confirm that these diseases are not caused by a second exposure to an allergen, which is a substance that can induce a hypersensitivity reaction in some people.
