L8 T Cell Immunity Flashcards
What are viruses?
Intracellular parasites
Examples of non-enveloped (naked) viruses:
Norovirus, Poliovirus
Examples of enveloped viruses:
Influenza virus, HIV (human immunodeficiency virus)
How do naked viruses work?
They infect the cell and cause cell lysis. The progeny viruses then escape
How do enveloped viruses work?
During infection, viral envelope proteins insert into the cell membrane of an infected cell. The progeny viruses then ‘bud off’
How can virus envelope proteins on the surface of an infected cell be targeted?
- Antibody/complement: lysis & phagocytosis
2. ADCC, leading to apoptosis
T cells only recognise short peptides (result from protein degradation in proteasome) when…
they are bound to MHC molecules on either APCs or infected cells
What is the main role of T cells?
eliminate microbes that survive inside cells
Do T cells recognise cell-associated or ‘free’ antigens?
cell-associated antigens (e.g. viruses and M. tuberculosis)
TCR α and β chains have a net __ charge
positive
How many other proteins is TCR non-covalently associated with?
5 other proteins (CD3 complex)
Transmembrane portions of ε 𝛾 δ ζ contain __ charged __ __ residues
NEGATIVELY charged ASPARTIC ACID residues
What makes up the ‘tri-molecular complex’
TCR/Antigen/MHC
What happens during thymic education?
Any T cells that could potentially attack our own ‘self-antigens’ on/in cells/tissues are eliminated
What cells are involved in the process of thymic education?
Interdigitating dendritic cells, cortical epithelial cells, macrophages
Thymocytes are derived from…
lymphoid stem cells
Positive selection of T cells for dual recognition of:
- Functional TCR on T cell surface
2. Recognises MHC molecules on APC surface
What does negative selection involve?
Deletion of ‘self-reacting’ T cells. Ff TCR recognises self-antigens, it is killed by APCs → apoptosis
Where does T cell education take place?
Thymus
Which chemokine attracts progenitors to the thymus?
CCL25
Which cytokine supports thymocyte proliferation?
IL-7
What do MHC and HLA stand for?
Major Histocompatibility Complex
Human Leukocyte Antigens
What genes are responsible for tissue/organ rejection?
MHC genes
Random recombination of V & J genes occurs in TCRs. Is this also seen in MHC genes?
No
The MHC genes are inherited as…
distinct genetic loci (you inherit one MHC copy from your mother and one from your father)
What are the 3 MHC Class 1 genes?
HLA-A, HLA-B, HLA-C (a single gene for each, producing a single α chain protein)
What are the 3 MHC Class 2 genes?
HLA-DP, HLA-DQ, HLA-DR (2 genes for each, producing an α chain & a β chain)
Every individual has their own set of MHC genes: True or False
True
How are MHC proteins expressed?
Co-dominantly expressed - 2 of each of the 6 types are expressed (HLA-A, HLA-B, HLA-C, HLA-DP, HLA-DQ, HLA-DR)
Are genes within the MHC chromosomal locus tightly linked?
Yes - this means that they’re inherited as a unit called a haplotype. We inherit one MHC haplotype from each parent (people are usually heterozygous)
Where are MHC I proteins expressed?
On the surface of all nucleated cells (they present self-antigens & virus antigens to CTLs)
Where are MHC II proteins mainly found?
On the surface of APCs (present foreign antigens to Th cells)
Does the MHC/peptide complex have a short or long half-life?
Long
What is the significance of each MHC having different amino acid residues in its cleft?
Different MHC alleles favour binding of different peptides
Proteins degraded in __ normally provide peptides for MHC Class I
proteosomes
Proteins degraded in __ provide peptides for MHC Class II
endo-lysosomes
To which cells can dendritic cells cross-present?
CD4+ Th cells, CD8+ CTLs
