Question

which of the following statements is/are true regarding failures of self - tolerance?
check all that apply
antibodies not only react against a pathogen but also against the bodies own cells.
upon exposure, antibodies may form against normal cells that blood does not usually become exposed to.
viruses may change the structure of self - antigens and cause the immune system to perceive them as foreign.
during anaphylaxis, allergens mimic normal cells and trick the immune system into making autoantibodies.
autoantibodies are introduced to the blood via transfusion.

Explanation:

• Antibodies not only react against a pathogen but also against the bodies own cells: In autoimmune diseases (failure of self - tolerance), the immune system (antibodies) attacks both pathogens (if present) and self - cells.
• Upon exposure, antibodies may form against normal cells that blood does not usually become exposed to: For example, in some cases of trauma (like testicular trauma), sequestered antigens (cells not usually exposed to the blood - immune system interface) are exposed, and the immune system can start attacking them.
• Viruses may change the structure of self - antigens and cause the immune system to perceive them as foreign: Molecular mimicry or virus - induced changes in self - antigen structure can lead the immune system to recognize self - antigens as non - self (foreign), which is a mechanism in failure of self - tolerance.
• During anaphylaxis, allergens mimic normal cells and 'trick' the immune system into making autoantibodies: Anaphylaxis is a type I hypersensitivity reaction (immediate hypersensitivity) mainly mediated by IgE and mast cells. It is not related to autoantibody production (which is more relevant to autoimmune diseases - failure of self - tolerance).
• Autoantibodies are introduced to the blood via transfusion: Autoantibodies are produced by the body's own immune system (in case of self - tolerance failure). Transfusion would introduce foreign antibodies (if it was antibody transfusion, but not autoantibodies).

Answer:

• Antibodies not only react against a pathogen but also against the bodies own cells.
• Upon exposure, antibodies may form against normal cells that blood does not usually become exposed to.
• Viruses may change the structure of self - antigens and cause the immune system to perceive them as foreign.