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.
What is immunological ignorance?
When antigens are not presented at sufficient levels to activate T cells.
What are immune-privileged sites, and give examples.
Sites where antigens are isolated from the immune system (e.g., eye, testis, CNS).
Why are there subsets of CD4+ T cells?
To mediate specific responses tailored to different pathogens.
Which cytokines promote TH1 responses?
IL-12 and IFN-γ.
What cytokines are important for TH2 responses?
IL-4.
What happens to CD8+ T cells after activation by APCs?
They develop into cytotoxic T lymphocytes (CTLs).
What are the organisms that infect interstitial spaces, blood, and lymph?
Viruses
Bacteria
Protozoa
Fungi
Worms
Name the organisms that infect epithelial surfaces
Neisseria gonorrhoeae
Mycoplasma spp.
Streptococcus pneumoniae
Vibrio cholerae
E. coli
Helicobacter pylori
Candida albicans
worms
What organisms can infect cytoplasmic intracellular sites?
Viruses
Chlamydia spp.
Rickettsia spp.
Listeria monocytogenes
Protozoa
Which organisms are responsible for infections in vesicular intracellular sites?
Mycobacterium spp.
Salmonella typhimurium
Yersinia pestis
Listeria spp.
Legionella pneumophila
Cryptococcus neoformans
Histoplasma
