Adaptive Immunity - T lymphocytes Flashcards
what is the role of specific immunity?
Recognise and respond to pathogen/danger. If it fails, then it’s death from infectious disease.
It needs to discriminate between self and non-self immune disease because if it starts attacking self then your having an immune reaction to your own cells which is autoimmune disease
Main types of T lymphocytes and their markers
where do viruses and some bacteria live and how can they be removed
in the cytoplasm of the cells. Once inside they can’t be detected by antibodies.
To remove these the infected cells have to be eliminated. This is done by CD8 cytotoxic T cells
what are naive T cells
cells that have not encountered antigen
What tissue type molecule do T cells use to (ID) recognise and respond to antigens that are inside cells
MHC - Major Histocompatibility complex found on nucleated cells. They have special grooves that antigen fragment slot into
CD8 T Cells, peptide & MHC I
CD4 T Cells, peptide & MHC II
How do antigens recognise T cells?
Peptide (antigen) recognise bound to MHC molecules on cell surface:
- infected/ abnormal cells (if a cell is infected the MHCmolecule is saying i’m infected kill me)
- antigen that has been processed then presented using MHC molecules on the cell surface of an antigen presenting cells (APC e.g. dendritic cells, macrophage)
(antigens can be put either on their own cell that’s infected or been gobbled up and they are alerting saying there’s a danger)
describe the structure of T cell receptor
similar to immunoglobulins part of superfamily
- constant region
- variable region
difference: the TCR remains membrane bound i.e. not secreted to do their job
they also have CDR ( complementary- determining regions) to bind to make ligands (antigen fragment that are processed in the cell and put on cell surface to bind to)
what molecules help T cell receptors transmit signal?
T cell receptor has another molecule called CD3 and an immunoreceptor tyrosine based activation motif (ITAM) to help with cell signalling.
These serve to help activate that T lymphocyte to help start the killing
what are the 3 types of gene fragments and what does it do?
Variable, Diversity and Joining
shuffling, cutting and pasting of gene segment - to produce infinite number of genes
What are the 2 forms of T cells receptors?
aB - alpha beta which is 90-99% of T cells
yS delta gamma - which is 1-10% of T cells helps with lysing certain cancers
how do T helper 1 cells work
T Helper 1 cells activate macrophages, which then kill viruses by phagocytosis. Then they work together to produce an immune reaction
what are Granulomas
clusters of immune cells that are formed in immune response e.g to infection, irritants, foreign objects
e.g. allergic to nickel or watch straps - can get rash due to granulomas
The concept of “T cell help” in B cells too
A cell e.g. a dendritic cell will process it’s antigen and display it on the cell surface with MHC (major histocompatability complex II ) and that will be recognised by a T helper cell that is specific for that particular antigen.
B cells can also act as APCs displaying antigen fragment using MHC II. They too can process antigen. B lymphocytes with the aid of the T helper cells and cytokines will then start producing antibodies.
B cells then become plasma cells and then start producing antibodies/ huge amounts of immunoglobulin
which become primary IgM or secondary IgG/E/A
T helper cells aid differentiation of a B cell into a plasma cells
what is Apoptosis
cell death (kills host cell so can’t make pathgoens)
difference of role between CD4 & CD8
CD8 cytotoxic T cells recognise
MHC I & Peptide on antigen-presenting cells - I am infected - KILL ME
CD4 Helper T cells recognise
MHC II & Peptide on antigen presenting cells - WATCH OUT - Danger about
MHC 2 names in man and mice
man - HLA - Human leukocyte antigens
mice - H -2
why do we not need a different MHC for every possible peptide antigen
cuz MHC molecules are encoded by the human genome and remain the same throughout life
describe the 2 types of MHC
MHC class 1
has 3 alpha chains and 1 beta
presents to cytotoxic T lymphocytes CD8
are only found on all nucleated cells
MHC class 2
has 2 alphas and 2 beta chains
presents to T helper cells CD4
are found on APC only antigen presenting cell
2 properties of MHC genes that maximise what it can do of peptides that can be bound
MHC genes are:
polygenic - an individual has several different MHC 1 and MHC 2 molecules encoded by genes in the MHC
Polymorpgic - there are multiple variants (alleles) of each gene in the population. Most individual are hetrozygotes
difference between peptide-binding to MHC class 1 and MHC class 2
class 1:
peptides 8-10 amino acids
bound at each end
different MHC class 1 molecules: different anchors
class ii:
peptides 13 plus (-17 amino acids)
not bound at the end
interaction along peptide with pockets on MHC: Anchors less defined
where are MHC proteins assembled
in the ER endoplasmic reticulum
- then intracellular antigen is broken down by fragments into smaller peptides
- then other transporters associated with antigen processing TAP responsiblefor ATP and using help of atp they then bind into becoming mhc class 1 molecule
one mhc class 1 has peptide in its groove it can be packaged and go into cell surface
