Immunology 1 Flashcards
List the 4 main functions of macrophages
1) Antigen presenting cells (APC) ingest and kill microbes -> PAMPS
2) highly phagocytic
3) clearance of RBC, WBC, apoptotic cells - DAMPS - damaged cells
4) Produce cytokines – signalling and amplification of immune response and colony stimulating factors – haematopoiesis
What are the 3 main killing mechanisms of neutrophils and examples of granules
3 killing mechanisms 1. phagocytosis 2. degranulation 3. NETs - neutrophil extracellular traps Primary (azurophilic) granules: - Larger, denser - Contain peroxidase, lysozyme, hydrolytic enzymes Secondary (specific) granules: - Smaller - Collagenase, lactoferrin, phospholipase
What are the 3 main areas mast cells are found and roles there
1) Gastrointestinal tract - important for parasites and worms
2) Airways - decreased diameter - prevent more pathogens from entering and increased mucus secretion - entrap the microbes
3) Blood vessels - as mast cells degranulate increase permeability of the blood - if get systemic infection can cause anaphylactic shock as too much leakage through blood vessels throughout body causing a decrease in blood volume and pressure
List 2 mediators from mast cells, basophils and eosinophils and their functions
Mast cells and basophils
1) histamine -> increase vascular permeability, stimulate smooth muscle contraction
2) Prostaglandin D2 -> Vasodilation, bronchoconstriction, neutrophil chemotaxis
Eosinophils
1) peroxidase -> degrades helminthic and protoxoan cell walls
2) leukotrienes C4 -> prolonged bronchoconstriction, mucus secretion, increased vascular permeability
What are Yδ T cells where found and function
mainly present in high levels in ruminants and neonatal animals
Only have a limited amount of molecules it can recognise unlike other T cells
List the 4 main anatomical and physiological barriers
1) Epithelial Barriers
- Skin and mucosal membranes, Tight junctions, keratin, apid turnover rates
2) Secretions
- Lysozymes, Antimicrobial peptides, oxidative radicals, Intraepithelial lymphocytes
3) Effector cells
- Macrophages, Neutrophils Mast cells, Eosinophils, Natural killer (NK) cells
4) Effector proteins
- Complement proteins, Acute phase protein eg Mannose binding lectin & C-reactive proteins
List the 6 features of the gut that acts as a barrier to infection
1) intestinal epithelial cells - physical
2) goblet cells -> produce mucus -> trapping
3) paneth cells -produce antimicrobial peptides and alpha defensins when given signals - cytokines -> insert themselves into membranes and form pores in the membranes that destroy the pathogen
4) M cells - sample intestinal lumen and stimulate cells within the peyer’s patches below if foreign material detected
5) Peyer’s patches
- lymphoid aggregates
6) Lamina propria
- Lymphocytes, B cells, dendritic cells, macrophages, plasma cells IgA
Describe the two main molecules that are involved with the activation of the innate immune system and give 2 examples
- Pattern-recognition receptors (PRR) expressed by cells of innate immune system and detect microbes
- Limited repertoire (recognize 103 molecular patterns) - Pathogen-associated molecular patterns PAMP = unique microbial molecules (PAMP) shared by groups of related microbes not found associated with mammalian cells.
1) Flagella protein
2) peptidoglycan from the cell wall
What are the 4 main types of PPR and main types within (example if needed)
1) Cell surface
1. Mannose receptor
2. scavenger receptor
3. N-formyl Met receptor
4. opsinon receptor
2) Cell surface signalling
- Toll-like receptors - TLR-4 (LPS)
3) endosomal
- other Toll-like receptors - TLR-3 (double-stranded viral RNA)
4) Cytosolic
- NOD like receptors
Cell surface PRR what are the 4 types of receptors and their function
1) Mannose receptor - bind lectins and mannose rich glycans
2) scavenger receptor - bind to bacterial cell wall components, LPS
3) N-formyl Met receptor - promotes motility and chemotaxis of phagocytes
4) Opsonin receptors - allows others to bind acute phase proteins, complement pathway, immune complexes
What are the functions of the PRR cell surface signallying and endosomal
1) Cell surface signalling
- TLR-4 recognise LPS
- Most use a intracellular signalling pathway within the cell that involves gene transcription of inflammatory cytokines and chemokines and antiviral chemicals such as interferons
2) Endosomal
- TLR-3 binds double-stranded viral RNA
- Activates same pathway as TOL-like receptors on the cell membrane
Cytosolic PRR what type of receptors where found and function
NOD-like receptors
Two main families of PRR recognize PAMps within cytosol.
Family of proteins involved in both PAMP (and DAMP) recognition and in cell signalling.
Include
1. NOD-like receptors (NLR) family of over 20 members) recognize peptidoglycan component of bacterial cell walls
- Regulate pro-inflammatory pathways via NFkB signalling via transcription
2. RIG - like receptors (RLR) family of 3 RNA helicases that detect viral RNA within cytosol.
- bind viral RNA (SS and DS)
- Activate NFkB signaling but also release interferons via transcription
What are DAMPs
- Associated with cellular and tissue injury and the result of release of cytoplasmic or nuclear molecules.
- DAMPs recognised by receptors against mitochondrial DNA, heat shock proteins ,adenosine metabolites, DNA interacting protein (HMGB1) .
What are the 3 functions of natural killer cells
1) Killing of injured cells - DAMPS
2) Killing of infected cells - altered MCH1 or altered antibody (binding to Fc receptor)
3) Killing of phagocytosed microbes
What are the 2 ways NK cells ill microbes
1) Via Fc receptor on the NK cell (Fcƴ RIII) - Antibody dependent cellular cytotoxicity (ADCC)
- Antibody is altered when binds to antigens on the surface of infected cells allowing NK cells to bind via their Fc receptor
2) Inhibitory and activating receptors
What is the mechanism for NK cells that allows some cells to be killed and others not
1) Inhibition
The cells have activating ligand that binds to the activating receptor on the NK cell
Normal cells have MHC class 1 receptors that bind to the inhibitor receptor on the NK cell which prevents NK cell from destroying healthy host cells
2) Activating
- Infected cells still have the activating ligand that bind to the activating receptor on the NK cell however the MCH class 1 receptor has been modified or downregulated due to viral or bacterial infection therefore inhibition doesn’t occur
- This leads to the activation of the NK cell and therefore lysis of the target cell
Structure of antibodies, what is the variable region, what gives functional change and what occurs
Basic antibody structure is composed of 2 heavy chains and 2 light chains
- The combination of a light chain with a heavy chain determine the antigen binding site -> variable region
- Once bound structure changes in the tail of the antibody so it can bind to Fc receptors, complements etc. ACTIVATED
Tail is giving the functional difference
what are the two main functions of antibodies
1) Neuralisation - prevent virus , bacteria and toxins from binding to key molecules on cell surfaces or within the body by blocking the binding region
2) Opsonisation - focus immune cells and complement to pathogens leading to phagocytosis or lysis of the pathogen depending on the immune cell it binds to.
List 5 innate immune cells that have Fc receptors and what occurs with opsonisation with Abs
1) Neutrophil - degranulation
2) Eosinophils - mainly IgE that binds to mast cell then binds eosinophils and causes degranulation
3) NK cells - leads to apoptosis of the cell via ADCC - Antibody-dependent cellular cytotoxicity
4) Macrophage - phagocytosis
5) Complement - activation causing
1. Lysis of microbes
2. Phagocytosis via opsonisation with complement fragments with C3b production
3. Inflammation
What are the 5 antibody isotypes and their general functions and what is the same about them
HAVE SAME ANTIGEN SPECIFICITY
Heavy chain determine isotype
1) IgM - pentamer -first response, antibody secretion, opsonisation
2) IgA - dimer - gut, resist pepsin cleavage, neutralisation to prevent movement through mucus membranes
3) IgE - parasites, allergic response (mast cells and eosinophils)
4) IgG - secondary response, opsonisation, neutralisation, can go across placenta
5) IgD - B cell receptor
What is different in terms of placental transfer in horses, ruminants and pigs, dogs and cats, primate and rodents and why
1) Horses, ruminants & pigs - epitheliochorial placenta - there are 6 barriers
- No transfer of Ab via placenta so colostrum extremely important
2) Dogs & cats - endotheliochorial placenta
- Only -5-10% IgG transferred via placenta
3) Primates, rodents - haemochorial placenta
- IgG transferred
What are the 6 barriers in epitheliochorial placenta
- Endothelial cells, connective tissue, epithelial - baby
- Epithelial cells, connective tissue, endothelial - mother
In what species and why are immunoglobulins in colostrum important, what type and timing that it occurs
Horses, ruminants & pigs - epitheliochorial placenta so no transfer during pregnancy
- when born no calf antibodies so need maternal from colostrum until can make their own
- IgM, IgG and IgA - neonates suckle (calf 2L colostrum)
- Absorption maximal in first 24h after birth due to epithelial cells not having tight junctions at that point
- Fc receptor on intestinal epithelial cells allow Ab to be transferred
Passive immunisation what does it result in and examples
Short-term as injecting the antibodies straight into patients so not creating own antibodies
EG - Snake-bite anti-venoms have concentrated Abs purified from serum of vaccinated horses