L15-Recognition of antigen by the adaptive immune system Flashcards
Through what processes do T and B cells develop a large range of antigen receptors?
Through combinatorial diversity which involves gene rearrangement of the different parts encoding the receptor. B cells undergo somatic hypermutation which further diversifies their receptors.
What is another name for MHC molecules?
HLA - human leukocyte antigens
Which cells recognise parts of antigens presented by antigen presenting cells?
T cells recognise these processed antigens as they can only recognise short peptide sequences and cannot recognise whole pathogens.
What do B cell receptors allow them to recognise?
Whole antigen on the cell surface.
What do plasma cells produce?
Soluble antigen receptors known as immunoglobulin molecules.
Where are MHC class 1 molecules found?
On all cells except neurones
What is the purpose of MHC class 1 molecules?
To present endogenous proteins to allow the recognition of infected cells for example viruses or cancers.
What cells bind to MHC class 1?
Cytotoxic CD8 T cells - the CD8 receptor acts as a co-receptor to the T cell receptor
What types of cells express MHC class 2 on their surface?
Dendritic cells, monocytes/macrophages and B cells
How do MHC class 2 molecules present processed antigens?
They internalise exogenous proteins so they can process them and present them on the MHC molecules
What cells bind to MHC class 2 molecules?
CD4 T cells - the CD4 receptor acts as a co-receptor to the T cell receptor.
What happens after a CD4 T cell binds to MHC class 2?
Depending on the cytokine environment the T cell either becomes an effector cell or a memory cell.
What are the two stages that B cells develop in?
Firstly within the bone marrow and then secondly in secondary lymphoid organs.
What is the basic structure of the antibody?
There are a pair of heavy chains and a pair of light chains. The heavy chains are connected by disulphide bonds and each heavy chain is connected to a light chain by a disulphide bond.
What are the two regions of the antibody?
The FAB region (fragment antigen binding) and the Fc region. The Fc region contains constant domains which are accessible to effector ligands following the formation of antigen-antibody complexes.
What is the best known accessory molecule on B cells and what is it for?
CD19 acts as a signalling molecule for when the antibody has bound to an antigen.
What is the variable region of the immunoglobulin made up of?
It contains three hypervariable regions which form the surface which binds to the antigen.
What are the two types of light chain?
Kappa or lambda
What is the structure of the T cell receptor?
It is composed of two non-identical Ig-domain polypeptide chains.
What are the two types of T cell receptor?
Either alpha and beta TCR chains or gamma and delta chains. CD4 and CD8 are co-receptors
What are the 4 different gene segments that make up the variable regions of immunoglobulins and t cell receptors?
Variable
Diversity
Joining
Constant
Which two enzymes are required to rearrange the genes for immunoglobulins
Recombinase activating genes (RAG-1 and RAG-2)
What can lack of the RAG enzymes cause?
This means that neither B nor T cells develop so can cause SCID.
Which step of gene rearrangement is first in forming immunoglobulins?
Combination of D and J segments, followed by the joining of the V segment to DJ.
