Immunology Flashcards
What are virus PAMPs?
Envelope, nucleocapsid, nucleic acid
Common building blocks: nucleic acids - ssRNA, dsRNA
What are the bacterium PAMPS?
Cell wall - lipopolysaccharide (LPS)/ endotoxins, lipoteichoic acid
Flagella: Flagellin
Nucleic acid: unmethylated CpG DNA
What occurs to activate the classical pathway?
Antibody bound to pathogen binds complement
Involves B cells making antibodies
What occurs to activate the alternative pathway?
Pathogen binds complement to surface/ pathogen component
Getting pathogen or pathogen component directly binding the complement
What occurs to activate the lectin pathway?
Carbohydrate components of microbes/pathogen bind complement
What is opsonization?
Labels/ coats pathogens which bind to complement receptors on phagocytes with C3b or/ and antibody
Means they can bind to complementary receptors on the phagocytic cell surface
The pathogen will then be phagocytosed
What is recruitment (inflammation)
Complement proteins act as peptide mediators of inflammation and recruit phagocytes
Mast cells degranulation by C3a and C5a (cells of the myeloid lineage, found in the tissues) - preformed granules that are important for inflammatory responses
Inflammatory mediators released including proteins that attract phagocytes to area of tissue inflammation.
Molecules that are attaching cells to the area but are also causing the capillaries to dilate and making the vessel walls leaky so the circulating immune cells can get out of the blood and into the area
What is destroy in the complement cascade?
Membrane attack complex formation: pores in bacterial cells → leads to death
Cell wall is broken down, contents can leak out and water can enter
Microbes coated with C3b are phagocytosed
Assembly of MAC complex causes lysis (Formed by complement protein which is primarily C9)
These insert into the target cell membrane and it develops a pore
What is MHC-1 and what does it present?
MHC-I presents endogenous (intracellular) antigen. Expressed on all nucleated cells Virus (Cytoplasmic antigen) growing inside the cell with produce peptides that are loaded onto MHC class 1 molecules
Peptides are imported into ER - loading onto MHC takes place, then are exported to the cell surface
What is MHC-2 and what does it present?
MHC-II presents exogenous (extracellular) antigen. Expressed only on antigen presenting cells.
Antigenic proteins are degraded in acidic phagolysosomes
Peptide loading takes place is phagolysosomes
What are the three functions of antibodies?
Neutralisation
Viruses usually need to attach to a receptor to attack the cell
Blocking the pathogen or toxic products from infecting host cells
Antibody binds to the virus and stops it from binding to the bodies cells
Could also be a toxins and neutralise them
Opsonization
Antibody will bind to microbes enable them to bind to a specific receptor on a phagocyte
Neutrophils, macrophages, dendritic cells
Complement activation
Formation of membrane attack complexes (and formation of pore)
Antibody bound to the surface of mirbe stimulates the binding of complement and in turn the activation of complement system
Further opsonization also occurs as well as formation of a pore
IgG
(monomer) Distribution Most abundant Ig class in blood Function Opsonises/ neutralises Only Ig class that crosses placenta: provides ‘passive immunity’ Protects unborn child that doesn't have a immune system Targets virus / bacteria
IgA
(dimer)
Distribution
Present in secretions such as tears, saliva, mucus, and breast milk
Monomeric form in blood
Function Defence of mucous membranes esp. Gut Present in breast milk Confers ‘passive immunity’ on nursing infant (IgA in milk transferred to infant) Targets virus / bacteria
IgM
(pentamer)
Distribution
First Ig class produced after initial exposure to antigen
Expressed on naive B cells
Function
Very effective in activating complement
Targets extracellular bacteria
Acts as antigen receptor (BCR)
IgE
(monomer)
Distribution
Present in blood at low concentrations
Function
Immunity to multicellular parasites
Allergic reactions (e.g. to poller or penicillin)
IgE activates mast cells for parasite immunity and the allergic response
