20 & 21- Regulation of Adaptive Immunity Flashcards
What is the definition of tolerance?
Immunological tolerance is the unresponsiveness of the immune system system to antigens
- dont want the body to react to self antigens
What is peripheral tolerance?
Mature lymphocytes that react to self antigens in peripheral sites such as lymph nodes and spleen
What is central tolerance?
Immature self-reactive lymphocytes in production sites such as thymus, bursa, or bone marrow
What is the result of negative selection during central T cell tolerance?
Deletion- if a T cell is reactive to self antigens, it will undergo apoptosis
What are the mechanisms of B cell tolerance in central and peripheral tolerance?
Central: Self-reactive B cells have a chance to go through 4 rounds of receptor editing to express a new Ig light chain= non-self reactive B cells, deletion leading to apoptosis, and the creation of an anergic B cell from reduced receptor expression and signaling
Peripheral: Induces anergy from functional inactivation, deletion leading to apoptosis, and regulation by inhibitory receptors
What are the mechanisms of T cell tolerance in central and peripheral tolerance?
Central: this includes positive and negative selection
Peripheral: this includes clonal anergy which is functional unresponsiveness, suppression which is blocking activation by a Treg, and deletion that results in apoptosis
How do antigens cause tolerance?
- tolerance is the name given to the situation in which the immune system will not respond to a specific antigen
- tolerance is primarily directed against self-antigens from normal tissues
- immune lymphocytes become tolerant to an antigen if they encounter it early in fetal life
What is anergy in T cells?
Refers to long-lived functional inactivation, the cells won’t proliferate, they just kind of exist
How does maternal immunity prevent successful vaccination of newborn animals?
The presence of maternal antibodies in a newborn animal effectively delays the onset of antibody synthesis
You should wait to vaccinate the young animal until the maternal antibodies are declining or in low levels. If vaccinated before this, it is a waste of the vaccine
What are some characteristics of Treg cells?
- Express CD4 and CD25 (when cell is naïve)
- Use specialized transcription factor FoxP3
- some of these develop naturally, but others must be induced by cytokines
What are some functions of Treg cells?
- play an important role in regulating the immune system and maintaining the balance between peripheral tolerance and immunity
- in their absence, multiorgan autoimmune disease results
- can also inhibit other cells like B cells and NK cells
What are the immunosuppressive cytokines?
IL-10
IL-35
TGF-B
What are the pro-inflammatory cytokines
IL-1
IL-6
TNF-a
How do Treg and TH17 cells regulate immune responses?
Tregs and TH17 cells both regulate immune responses via the cytokines they release
TH17 cells secrete IL-17 which act on neutrophils and cause large amounts of inflammation
Activated Treg cells secrete immunosuppressive cytokines (aka anti-inflammatory molecules)
IL-10 suppresses most cell types but enhances Treg cells, TGFb regulates macrophages, B cell function and T cell activation
What is immune deviation?
A phenomenon in which an adaptive response that has the potential to cause direct or indirect tissue damage is converted to a less harmful response
