4. Adaptive Immunity: T-cell Response Flashcards
LOs
FC SET NOT COMPLETE - USE QUIZLET
· Outline the functions of helper T cells (Th) and cytotoxic T cells (Tc)
· Describe antigen processing and T cell recognition of processed antigen complexes with proteins of the major histocompatibility complex/human leukocyte antigen (MHC/HLA)
· Describe how T cell antigen receptor diversity occurs
· Outline the processes of positive and negative selection of T cells in the thymus that determine effective T cell function
- what is adaptive immunity?
- major components of adaptive immune response?
1.
- acts as a second line of defence if the innate
immune system is ineffective at dealing with pathogens
2.
- T + B lymphocytes
- This type of immunity is antigen specific
- Memory cells are also involved in this immune response hence = longer lasting + more effective
where do cells of the immune system derive from?
- cells from the immune system derive from precursors in the bone marrow
T cell precursor origin?
migrate to?
- in bone marrow
- T cell precursors migrate to thymus where
they maturate - (in thymus, precursor cells = thymocites)
T cell types?
A - function classes
B - functions
- Cytotoxic T cells (Tc) or CTL
A - killing
B - kill cells infected with viruses or other intracellular pathogens
- T helper (Th) cells
- Th1 Th2,Th17
A - activation
B- provide essential signals that activate B- cells, macrophages + other T cells
- Regulatory T cells
- (Tregs)
A - regulation
B - suppress the activity of other lymphocytes + help control immune responses
T cell function classes
- killing
- activation
- regulation
- helper T-cell functions?
- what mediates immune cell activation?
1.
- regulate the adaptive immune response
- regulate activation of immune cells (T cells, B cells, granulocytes, macrophages and dendritic cells)
2.
- Activation of immune cells is mediated by cytokines released by Th cells
- Innate + adaptive immune responses combine to fight infection
- Innate hold the pathogen back until adaptive kicks in (can be few days)
- innate = essential prevent spread of infectious agents
what are cytokines?
• secreted proteins including growth and differentiation factors as well as chemoattractants
• bind to specific receptors on surface of target cells and initiate cell signalling (hormone-like)
- induce expression of genes required for activation + proliferation +production of further cytokines + cell migration
• standardised nomenclature – “interleukins” (IL) Numbered in order of discovery IL-1, IL-2 ….IL-41
• 20 chemokines have agreed names (chemoattractant cytokines), Interferons (IFN)-α, β, γ; Transforming Growth Factor (TGF)-β, Tumour Necrosis Factor (TNF)-α etc…
• Secretory T cells and target cells in close contact
what do cytotoxic t lymphocytes do?
Acts as an effector cell in the immune response
Recognises cells that are infected by intracellular pathogens induce, apoptosis
Does that in 3 ways mentioned
Fas is a death receptor
In all cases the outcome is
cell death
how do T cells recognise antigens? (add more?)
(i)
- T cell antigen receptors do not bind directly to antigen
- only recognises modified forms of antigens that are bound to surface proteins
- this form of antigen recognition results in close contact of t cells + cells that secrete cytokines + target cells
- this helps to ensure that cytokines are efficiently targeted to the correct cells
(ii)
- 2 types of MHC
class I + II
(iv)
how do T cells recognise antigens?
(i)
how do T cells recognise antigens?
(ii)
how do T cells recognise antigens?
(iii)
how do T cells recognise antigens?
(iv)
MHC class I+II features
- expressed by?
- gene loci?
- polymorphic?
- what binds to this class?
Summary of section 1
T helper cells and cytotoxic T cells
