Which of the following conditions may lead to the development of autoimmunity?


a. Self antigens not previously encountered by T cells are released into the circulation
b. Foreign antigens mimic self antigens
c. Cells may inappropriately display class II MHC molecules
d. Certain pathogens nonspecifically activate B cells
e. All of the above are correct

Verified step by step guidance

1. Step 1: Understand the concept of autoimmunity. Autoimmunity occurs when the immune system mistakenly targets the body's own tissues, recognizing self-antigens as foreign and initiating an immune response against them.
2. Step 2: Analyze option (a): Self antigens not previously encountered by T cells are released into the circulation. This can lead to autoimmunity because T cells may recognize these antigens as foreign and attack them.
3. Step 3: Analyze option (b): Foreign antigens mimic self antigens. This phenomenon, known as molecular mimicry, can cause the immune system to attack self tissues that resemble foreign antigens.
4. Step 4: Analyze option (c): Cells may inappropriately display class II MHC molecules. Class II MHC molecules are typically displayed by antigen-presenting cells, but if other cells display them incorrectly, it can lead to the activation of T cells against self-antigens.
5. Step 5: Analyze option (d): Certain pathogens nonspecifically activate B cells. This nonspecific activation can lead to the production of autoantibodies, which target self-antigens, contributing to autoimmunity. Finally, evaluate whether all options (a, b, c, d) are correct, as suggested by option (e).

Key Concepts

Autoimmunity

Autoimmunity occurs when the immune system mistakenly targets and attacks the body's own tissues, leading to various autoimmune diseases. This can happen when the immune system fails to distinguish between self and non-self antigens, resulting in an inappropriate immune response against the body's own cells.

Molecular Mimicry

Molecular mimicry refers to the phenomenon where foreign antigens share structural similarities with self antigens, causing the immune system to attack both the pathogen and the body's own tissues. This can lead to autoimmune responses, as the immune system cannot differentiate between the two due to their resemblance.

MHC Class II Molecules

MHC Class II molecules are proteins found on the surface of certain immune cells that present antigens to CD4+ T cells. Inappropriate display of these molecules can lead to the activation of T cells against self antigens, contributing to the development of autoimmunity by promoting an immune response against the body's own cells.