Lecture 43 Flashcards
What are the main functions of the adaptive immune response?
The adaptive immune system is what acts to destroy pathogens which the innate immune system could not, the adaptive immune system is also responsible for “memory” of pathogens, hence allowing for vaccines to work and giving immunity to pathogens we have recovered from.
What are dendritic cells?
A type of cell which sits within many tissues, particularly those exposed to external surfaces. If it detects a pathogen it will collect the pathogen, break it down and carry it to the lymph nodes for interaction with T and B cells.
What are the two main cells in the adaptive immune response? Which one of these splits into two subgroups?
The two main cells are B cells (produce antibodies) and T cells, the T cells consist of the CD4+ and CD8+ cells, the CD4+ will help the B cells and CD8+ cells achieve their function, the CD8+ cells become cytotoxic (CTL) allowing them to kill virus infected or cancer cells.
What is an antigen? What types are there? Why are they taken up?
Anything that has the potential to be recognised by the immune system, these can be either foreign antigen (e.g transplants, pathogens, some chemicals) or auto-antigens, these are antigens the immune system normally tolerates because they belong to our cells, they may however be recognised in autoimmune disorders. They are taken up for clearance of pathogens (innate response) or for presentation to T cells (adaptive response).
What is MHC? What are the types?
Major histocompatibility complex (MHC) is a compound found on the outside of cells which presents antigen peptides to antigen specific T cells. There are two types, MHC-I presents endogenous (intracellular produced, typically for viruses or cancer) antigens and is expressed on all nucleated cells (including antigen presenting cells).
MHC-II presents exogenous (produced outside the cell) antigens. Expressed only on antigen presenting cells like dendritic cells (for phagocytised pathogens).
What structures does the MHC contain?
Contains 4 parts which make up the protein, alpha1, beta1, beta2 and alpha2. The peptide binds in the peptide binding cleft which is located between the beta1 and alpha1 parts. The antigen peptides are held in place by hydrogen bonds.
How are endogenous and exogenous antigen peptides loaded?
Endogenous: antigenic proteins produced by the endogenous antigen (typically a virus) are degraded to peptides in the cytoplasm, these peptides are then imported into the endoplasmic reticulum and peptide loading of MHC-I takes place on the endoplasmic reticulum.
Exogenous: exogenous antigen is phagocytised, antigenic proteins are degraded in the acidic phagolysosome and peptide loading of MHC-II also occurs in the phagolysosome.
Where did the adaptive immune response evolve?
In vertebrates about 500 million years ago.
What is an antigen peptide?
Fragments of proteins produced by that antigen
