Regulation of acquired Immune System Flashcards
lecture 7
Why is immune tolerance required?
To prevent autoreactivity caused by random BCR/TCR generation.
What happens to T cells that fail to recognise self-MHC?
They die by neglect (no positive selection survival signals).
What does negative selection of T cells in the thymus achieve?
It removes T cells that bind self-MHC + thymic peptides with high affinity.
What is the role of AIRE protein in T cell tolerance?
It allows expression of tissue-specific antigens (TSA) in the thymus, enabling deletion of self-reactive T cells.
What happens in AIRE deficiency?
It causes autoimmune syndromes like APECED.
What are the fates of immature B cells recognising self-antigens in bone marrow?
Clonal deletion, receptor editing, or anergy.
What is receptor editing in B cells?
A process where B cells rearrange their light chain genes to remove self-reactivity.
What is the function of Tregs?
Suppress immune responses to prevent autoimmunity.
What transcription factor is crucial for Tregs?
FoxP3.
What do regulatory B cells (Bregs) secrete, and why?
IL-10, to dampen immune responses and prevent autoimmunity.
What are TH1 cells responsible for?
Activating macrophages, NK cells, and cytotoxic T cells.
Which subset of CD4+ T cells promotes IgE production?
TH2 cells.
What do TH17 cells secrete and what is their function?
Secrete IL-17; recruit neutrophils for fungal infections and are implicated in autoimmunity.
What is the role of TFH cells?
Help B cells in germinal centres to produce antibodies.
What mechanisms ensure T cell anergy?
Signal 1 without signal 2 (no co-stimulation) leads to an unresponsive state.
