Immunology 3 ( T Cell Mediated Immunity) Flashcards
Do T cells produce antibodies?
No
Do T cells produce secreted TCRs
No
What family are TCRs and Immunoglobulins members of?
The immunoglobulin superfamily
True are false: the variable domain on each t-cell differs?
True
Describe the make up of a T cell receptor.
Alpha chain and beta chain. Constant alpha and variable alpha and constant beta and variable beta
How do helper T cells help B cells?
Help them differentiate into Ig secreting plasma cells
How do helper T cells help macrophages?
Activates them so they can carry out phagocytosis and killing
What at T cells relationship with APCs?
T cells can not interact directly with antigens can only interact with antigens presented on cells (APC)
What is the only type of antigen T cells will recognise?
Proteins
What allows the antigen peptide to be presented on APCs?
A surface membrane protein called HLA in humans MHC in mammals
What is the mhc1 receptor made of?
Alpha 1,2,3 and a beta micro globulin
What type of T cells bind to HLA class 1 cells?
Cd8 cytotoxic T cells
What is the HLA class ii receptors made of?
Beta 1,2 and alpha 1,2. ( the 1’s are closest to the antigen)
What T cells bind to HLA class 2?
Helper T cells
What are the helper proteins for HLA-t cells interactions?
Cd4 (helper) and cd8 (cytotoxic)
What is cd8 made of?
Two polypeptide chains that bind to alpha 3 of the HLA class 1
What is cd4 made of?
It is a single polypeptide but with 4 immunoglobulin like domains ( part of superfamily) that bind to the side of the beta 2 domain of HLA 2
What are protein antigens in the cytoplasm degraded in?
A complex called a proteosome
How are peptides transferred the proteosome to the endoplasmic reticulum?
Via peptide transporter proteins.
What length are the processed peptides?
8 or 9 aa
Where do the processed peptides meet the newly synthesised HLA 1?
In smooth endoplasmic reticulum via peptide transporter gateways. Once complex they move to the surface
What happens after enocytosis of exogenous particles?
Internalised into a vacuole. Enzymes entering the vacuole degrade the antigen.newly synthesised HLA 2 is transported to vacuoles and complexed with antigen peptide aa
What processing do infected cells do?
HLA class 1 processing
What do B cells that have taken in bound antigen do?
HLA type ii processing- helper T cell comes and turns B cell into a plasma cell
Can most cells process HLA 1 and 2?
Most cells type 1
Mostly immune cells type 2
What types of cells express high levels of type HLA type 1 and 2?
Dendritic cells
What are cytokines?
Secreted proteins that regulate cellular activity
Which helper cells can promote allergic reactions?
Th2
How does th2 activate mast cells and eosinophils during an allergic reaction?
Th2 produce IL-4 which promotes B cells to produce IgE which binds to mast cells priming them to release inflammatory mediators.
Th2 produces IL-5 which activates eosinophils
Why/How are giant cells formed?
TB. Micro bacteria engulfed but can’t be killed. Macrophages stimulate th1 cells to produce TNF-gamma to stimulate more macrophages. Macrophages differentiate into epitheloid cells that fuse to become multi-nuclear giant cells.
In an X-Ray of someone with TB what would you see?
Shadowing over the lungs due to inflammatory tissue damage caused by activated macrophages and tissue damage
In a TB tissue section what would you see?
Massive t-cell infiltration, giant cells and epitheloid cells and destruction of tissue architecture
How many types of leprosy is there?
- One is th1 responsive and the other is th2 responsive
What is th1 responsive leprasy called?
Tuberculoid leprasy - mainly th1, IFN-gamma. Killing of microbacteria
What is th2 responsive leprasy called?
Lepromatous Leprasy . Lymphocyte infiltration only- can’t kill microbacteria
What do you call the affinity of some viruses to particular receptors?
Tropism
What do you call viruses with no envelope?
Lytic viruses- kill cell
What do you call viruses with an envelope?
Budding viruses- do not kill cell- form part of cell membrane
Name the 7 stages of a virus life cycle
1) infecting virus
2) attachment to cell receptors
3) penetration
4) uncoating
5) replication
6) assembly capsid
7) release
What can antibodies alone do to stop viruses?
They can block binding and entry into cells
What can antibodies and complement do to protect from viruses?
Damage to enveloped viruses and opsonisation for phagocytosis
What proteins are used to define influenza A viruses?
Capsid proteins. Haemagglutinin (H) and Neuraminidase(N)
What causes virus drift?
Small mutations- replication errors
What causes Shift?
When two strains of influenza virus recombine forming a new strain.
What is the antiviral action of interferons?
Interferon alpha and beta produced by infected cells results in activation of enzymes in cells to degrade viral mRNA
What are NK cells?
Large granular lymphocytes
Can NK cells recognise antigens?
No. But they have FC receptors for IgG antibodies.
What do NK cells bind to on cells?
Two receptors - kill and don’t kill
What does the inhibitory receptor on NK cells bind to?
HLA class 1.
How can a NK cell if another cell is abnormal?
Reduced expression of HLA class 1
What happens tumour cell expression of HLA class 1?
It is reduced
What interferon do NK cells produce?
Type 2 Interferon gamma. - enhances HLA class 1 and class 2 expression
What two types of proteins are released from granules in NK cells?
Perforins- perforate surface cells and form structures in cell membrane (similar to c9)
2) granzymes. Activate the cells own apoptosis enzymes
What are caspases?
The cells apoptosis enzymes -activate endonucleases
What is the second way infected cells can activate NK cells?
By expression Fas ligand- induces apoptosis
