The nature of immunity Flashcards
What are the most important features of the immune system? (3 answers)
specificity, memory and self-discimination
What are the 2 main responses to a pathogen?
recognition (location of the pathogen + the type of pathogen) and defence
what are the physical barriers of the body? (2 answers)
skin and mucosal areas (e.g. sinuses, eyes, oral cavity)
2 steps of the innate immune response
recognition of the pathogen and the recruitment of effector mechanisms that kill and eliminate the pathogen
what are polymorphonuclear cells and which ones exist?
also callled granulocytes - because the cells contain granules. basophils (acidic granules - bind to basic stains e.g. haematoxylin), eosinophils (basic granules - bind to acidic stains e.g. eosin) and neutrophils (granules dont bind to neither of the stains)
what is the most abundant cell type in the body?
neutrophil
What is the main function of neutrophils?
the effector cells of innate iummune response - they are the first ones to be recruited to sites of infection + can work in anaerobic conditions ( often the case of damaged tissue)
What are the products of neutrophils?
azurophilic granules
which cell type contains azurophilic granules and what is inside the granules? (4 answers)
neutrophils. the granules contain enzymes - myeloperoxidase and lysozyme, bactericidal/permeability-increasing protein, cationic proteins - alpha defensins, cationic glycoproteins -serprocidins
what is the bactericidal / permeability-increasing protein and what isits function?
antibiotic protein with potent killing activity against gram-neg bacteria (it binds to LPS produced by bacteria
what is the function of cationic proteins i.e. alpha defensins?
killing activity against many gram-negative, gram-pos, fungi and enveloped viruses
what cytokines do neutrophils secrete?
IL-1, -6, -8, TNF-alpha, colony-stimulating factor (CSF), IFN-alpha
what is the main function of eosinophils?
defence against helminth worms and other intestinal parasites (when the pathogens are too large to be phagocytosed)
which products of eosinophils are pre-formed?
enzymes (eosinophil peroxidase - triggers histamine production, and eosinophil collagenase - remodelling of connective tissue) and toxic proteins (major basic protein - toxic to parasites and mammalian cells + triggers the release of histamine, eosinophilcationic protein - toxic to parasites, neurotoxin)
which products of eosinophils are newly synthesized?
cytokines
how do eosinophils recognize a parasite?
eosinophils express FcεRI - receptor which recognizes IgE opsonized parasites
what is the mechganism of action of eosinophils?
extracellular digestion
what mononuclear cells can be found in the body?
monocytes, macrophages, dendritic cells
what is the structure of a macrophage?
large, irregularly shaped cells with a huge cytoplasm containing numerous vacuoles (perfect for phagocytosis)
in what specialized tissues can we find macrophages and what are their other names?
macrophages in neural tissue = microglial cells, liver = kupffer cells
what are the similarities and differences between macrophages and neutrophils?
both have a phagocytic function, the biggest difference is that macrophages are tissue-resident cells (everywhere in the body) and neutrophils migrate to the site of infection once they sense cytokines
what are the receptors expressed on macrophages?
mannose receptor, dectin-1, scavenger receptor, lipid receptor, complement receptor, and FcεRI
what happens to material that is recognized by macrphages?
bound material os internalized in phagosomes and broken down in phagolysosomes
how are the enzymes within the lysozyme activated?
the pH changes once the macrohage binds a material - activating the enzymes inside
what is the function of plasminogen activator
digestion of tissues - easier migration for the immune cells
main function of dendritic cells
recognition, engulfment and presenting pathogens to T cells
normal function of mast cells (2 things)
major contribution to inflammation - defence against parasites and some types of bacteria
what pre-fromed mediators do mast cells contain?
histamine, heparin proteoglycan, chemotactic factors (ECF and NCF), acid hydrolases (beta-glucuronidase, phosphatase), neutral protease (tryptase, chymase)
what is the function of histamine
vasodilation + very rapid recruitment of other leukocytes
2 ways of how mast cells can be activated
by complement or PRR/PAMP signalling
what are the 2 lineages of lymphocytes (+ what cells belong into each lineage)
lymphocytes are divided morphologically - large lymphocytes with a granular cytoplasm (NK cells) and small lymphocytes with almost no cytoplasm (T and B cells)
main function of NK cells
(effector cells of innate immune response) main defence against viral infections
2 types of adaptive immune response
humoral - facilitated by B cells and cell-mediated facilitated by T cells
when is humoral immunity activated
in response to extracellular pathogens -> mostly bacteria and parasites
what are the primary lymphoid tissues
bone marrow and thymus
secondary lymphoid tissues
spleens, adenoids, tonsils, appendix, lymph nodes, peyer’s patches (in the small intestine
2 defensive mechanisms of antibodies
neutralization and opsonization
describe neutralization by antibodies
when the Ab binds to the toxic compound - this prevents the toxin from interacting with its receptor on human cells
what is a draining lymph node
the lymph node receiving fluid collected at an infected site (the closest lymph note to the infection, where the APCs go and present pathogens)
2 most important functions of NK cells
killing the pathon and maintain / increase the state of inflammation in the infected tissue (secretion of inflammatory cytokines)
how to differentiate NK cells and T cells
all NK cells express CD56 (unknown function) and they lack CD3 (expressed by T cells only)
how to differentiate NK cells and T cells
all NK cells express CD56 (unknown function) and they lack CD3 (expressed by T cells only)
how are NK cells regulated? (3 safety features)
- NK cells cannot release their lytic granules from a distance = contact with the infected cell
- multiple receptors need to bind to their ligands for the NK cell to be activated
- they can be only activated when their inhiibitory receptors are inactivated (activating receptors also need to be activated)
what cytokines are released from virally-infected cells and what cells do they act on
INF-alpha and -beta -> first cytokines that act on NK cells
