Adaptive Immunity 1 Flashcards
What is the cellular and humoral components of adaptive immunity?
T cells - cellular
B cells - humoral
When is the adaptive immunity activated?
after 4-7 days
What does the threshold level mean?
the amount of pathogen present to mediate an immune response
What are the the 3 main receptors of the adaptive immune response?
T cell receptor
B cell receptor
Major Histocompatibility Complex (MHC)
What is the difference between the innate receptors (TLR) and adaptive receptors?
innate receptors cannot change shape to identify different antigens
adaptive receptors can rearrange structure depending to gene expression of each protein subunit.
How do T cells recognise peptides?
via TCR and MHC interations
Where do T cells mature?
thymus
What does Tregs balance?
pro- and anti- inflammatory responses
they dampen down immune responses
What are the subsets of T cells?
CD4+
CD8+
Tregs
What is the receptor for CD8+ and what does it bind to?
CD8
MHC 1
What is the role of MHC 1?
alerting the immune system to virally infected cells.
What is the receptor for CD4+ and what does it bind to?
CD4
MHC 2
What is the role of MHC 2?
for APCs presenting antigens from microbes such as bacteria, fungi etc.
What is the receptor involved in the activation of both CD4+ and CD8+?
CD3
What are the two classes of T cell receptor?
Alpha
Beta
What classes of T cell receptor do a small portion (around 5%) of T cells express?
Gamma
Delta
What are the two regions of the chains?
Constant
Variable (changing)
What are the 3 gene segments of the variable region and what do they encode?
V (variable) (both α and β chains)
D (diversity) (β chain only)
J (joining) (both α and β chains)
By what process are genes rearranged to identify new pathogens?
somatic recombination
What is somatic recombination driven by?
RAG (recombinase enzymes)
What do T cells interact with in the thymus?
pass by thymic cortical epithelial cells and interact
Describe the two processes of thymic education
Positive selection - if cells cannot recognise self-peptides, they die. if they do they move to negative selection
Negative selection - if cells bind too strongly to self-peptides, they die
Where do T cells immigrate to after education?
circulating blood
lymph nodes
lymphatics
What do the three signals do to the T cell?
signal one = activation of T cell
signal two = survival and clonal expansion of T cell
signal three = differentiation into subsets of effector T cells (specifically for CD4+ helper T cells)
What are the three signals that prime T cells?
1’ MHC-TCR interaction
2’ co-stimulatory molecules interactions (CD80/CD86 and CD40 on DC —- CD40L and CD28 on T cell)
3’ signal dictates what T helper cell the naïve cell becomes.
What is signal 1 but no signal 2 known as?
anergy
What does the third signal lead to in CD8+ cells?
the third signal leads to effector function e.g., production of enzymes for degradation
What enzymes induce target cell apoptosis?
perforin
granzyme
What does interferon-γ do?
instructs immune cells such as macrophages and cytotoxic T cells to destroy infected cells.
What is the role of TH1 cells?
Main role in supporting macrophage function
Source of interferon-γ
What is the role of TH2?
Supporting plasma B cell responses and allergic reactions - activates mast cells and eosinophils
Source of IL-4, IL-5 and IL-6
What do IL-4, IL-5 and IL-6 do?
instructs B cells to produce antibodies
What is the role of TH17?
Main role in supporting innate immune responses
Enhances clearance of extracellular bacteria and fungi
Produces IL-17 and IL-22
What does interleukin-17 do?
stimulate epithelial cells to produce antimicrobial peptides
What is the role of TFH?
T follicular helper cells are found in secondary lymphoid organs in B cell zone (not T cell zone)
Work together with B cells for antibody production
Produces IL-21
What does interleukin-21 do?
drives B cell proliferation
What is the role of Treg cells?
Regulatory T cells that function in immune suppression
Release inhibitory cytokines IL-10
Inhibit T cell activation and dendritic cell activation
What is the role of CD8+ cells?
Activation arises from interactions between MHCI and TCR
Induce host cells to undergo apoptosis (programmed cell death)
Produces enzymes such as granzyme/perforin
What does loss of TFH cells mean?
loss of T follicular helper cells leads to dysfunctional antibody production in germinal centre of lymph nodes
