Perturbations in the Super System Flashcards
What are superantigens?
In contrast to conventional peptides that require uptake and processing prior to presentation by T-lymphocytes, superantigens interact with the “side” of the MHC Class II-TCR complex
-Effectively, they cross-link MHC Class II to T-cell receptors
Give two examples of superantigens
Toxic Shock Syndrome Toxin-1 (TSST-1) and Staphylococcal enterotoxin (SE)
What follows in response to superantigen binding?
Cytokine storm: polyclonal extensive activation of T cells leads to the over-production of TNFalpha (and IL-1/6)
Which are the 4 hallmark signs of toxic shock syndrome?
Fever, hypotension, rash, desquamation (1-2 weeks after illness, particularly involving the palms and soles of your feet)
Toxic Shock Syndrome is caused by toxin released from what bacteria?
Staph Aureus
The clinical manifestations of TSS are precipitated by what immune response?
Cytokine storm —> disease
Causes low blood pressure, fever, diarrhea, shedding of skin
CCR5 deficient individuals are resistant to what virus, but very susceptible to what other virus?
Resistant to HIV
Susceptible to West Nile Virus
What is CCR5?
CCR5 is a chemokine receptor for chemokines that attract and direct the migration of T cells to the site of infection
CCR5 is located ON the T cells
Why are CCR5 deficient individuals resistant to HIV?
CCR5 is a co-receptor (along with CD4) for binding and entry into human T-lymphocytes by HIV-1
Why are CCR5 deficient individuals susceptible to west nile virus?
They are susceptible because T-cells cannot taxi to the site of infection, as they cannot follow the CCR5 signal
What is the most cytokine produced by virally infected cells?
Interferons.
Interferons then activate macrophages, dendritic cells, they drive a Th1 response (CD8+, B cells) and NK cells
In contrast to most viruses, certain viruses have the capability of directly inducing IL-10 (such as HIV). What is the consequence of this?
IL-10 is very immunosuppressive.
This reduces the capacity of DCs and macrophages to wage war, drives a Th2 response, and reduces the immune response in general
How does the herpes virus suppress the immune response?
The herpes virus has acquired human IL-10 in their genome, so when they infect a cell and start to replicate, they produce immunosuppressive IL-10
List 4 ways viruses can alter chemokine function to benefit their survival
1) Chemokine secretion attracts susceptible cells for further infection
2) Chemokine secretion attracts infected cells to distant tissues
3) Chemokine receptor function or expression may be inhibited
4) Chemokines and/or receptors may be sequestered inside the cell
Autoimmune diseases are caused by self-reactive what?
T and B lymphocytes
How do genetics play a role in autoimmune diseases?
Some people are genetically predisposed to autoimmune dysfunction
Females are disproportionately affected by autoimmune diseases (3:1) (after puberty- sex hormones contribute)
Also, females have a more vigorous Th1 response to antigen and more successfully produce antibodies
Peripheral tolerance is enforced by which cells?
CD4+25+ FoxP3+ T regs
