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- natural immunity
- treats all foreign objects the same
what is amensalism
one species restricts growth of the other
what characteristics of the skin aid in innate immunity?
- dry, salty, low pH (5-6)
- continuous shedding
- covered with normal micorbiota
what characteristics of the mucous membranes aid in innate immunity?
- protective layer of mucus traps microbes to be swept out by cilia
- bathed in antimicrobial peptides
what characteristics of the respiratory system aid in innate immunity?
- expels microbes by coughing or sneezing
- salvation washes microbes to stomach
- alveolar macrophages
what characteristics of the GI and GU tracts aid in innate immunity?
- low pH
- normal flora restrict the growth of pathogens
what are the 4 chemical barriers that aid in innate immunity
- gastric juices
hydrolyzes bonds between sugars in peptidoglycan leading to bacterial lysis
mix of HCL, proteolytic enzymes and mucus that has a pH of 1-3
produces superoxide radicals that damage microbes
sequesters iron limiting microbe replication
how do antimicrobial peptides work?
kill microbes by interacting with their membranes
what are the 2 major types of antimicrobial peptides?
cationic and bacteriocins
what do most cationic peptides do to kill microbes?
most form pores of transient gaps, thereby altering membrane permeability often leading to lysis
what are the 3 generic classes of cationic peptides?
- cathelicidin - linear alpha helical peptides
- defensins - rich in arginine and cysteine that stimulate mast cell degranulation
- histatin - larger peptides that have regular structural repeats and has anti fungal activity
what are bacteriocins?
antimicorbial peptides that are produced by bacteria to kill other species of bacteria
where to NK cells originate?
in the bone marrow
what do NK cells do?
kill malignant cells and cells infected with pathogens by releasing cytotoxic granules resulting in direct lysis of the target cell
how are NK cells activity governed?
by the integration of activating and inhibitory signals from cell surface receptors
what is the mechanism of target cell recognition and lysis?
1. ADCC - antibody -dependent cell mediated cytotoxicity relies on Fc receptors
- 2. loss of MHC class 1 on the target cell
- 3. presence of activating ligand
circulate int he blood and migrate to sites of tissue damage because they contain substances that kill microbes and enhance inflammation
what are the three types of granulocytes?
- most abundant WBC
- rapidly responds to infection
- highly phagocytic
- kill ingested microbes with lytic enzymes and reactive species
- migrate to musous membranes
- control helminth infections
- role in allergy and hypersensitivities
- release vasoactive mediators (histamine, prostaglandins,serotonin, leukotrienes
- role in allergic responses
circulate in the blood, then migrate to tissues where they mature into macrophages or dendritic cells
- reside in specific tissues
- highly phagocytic
dendritic cells (DCs)
have long dendrites that capture foreign particles to phagocytose. The antigens are processed to display on their surface for T-cells (antigen presentation)
engulfs the microbe where it is digested by lysosomal enzymes
what are the functions of the complement system?
- defend against infection
- provide chemotactic signals that recruit phagocytes to their site of activation
- puncture microbial cell membranes causing cell lysis
- complements the antibacterial activity of an antibody
describe the process of opsonization
microbes are tagged with serum proteins (opsonins) that lead to their recognition and ingestion by phagocytic cells
what are some common opsonins?
- complement proteins
- mannose binding protein
what are the 3 pathways through which complement proteins are formed?
- classical pathway--> C3a + C5a
- MB-lectin pathway --> C3b
- alternative pathway --> terminal complement components C5b, C6,C7,C8,C9
cleaves C3 to make complement proteins
where is activation confined to in complement proteins?
confined to the pathogen surface
MAC (membrane attack complex)
a tubular structure that forms a transmembrane pore in the target cells membrane so that H2O and Na+ can enter leading to lysis
what are cytokines?
- soluble proteins that are released by one cell and act on the same cell or on other cells
- they induce a signaling cascade
they are cytokines that function as chemoattractants to recruit immune cells to sites of infection
type 1 interferons
- primarily involved in antiviral immunity
- prevents viral replication and assembly
- characterized by their autocrine and paracrine activity
steps for IFN -alpha/beta immunity
- 1. virus infects cell
- 2. activates IFN gene
- 3. infected cell synthesizes IFN and releases it to neighboring cells
- 4. activation of antiviral proteins in uninfected cells before virus invades a new cell
type 2 interferons
involved in immunity against many types of infections
cytokines that elicit fever in the host
what are the steps for endogenous pyrogen induced fever?
- 1.a macrophage ingests a gram-negative bacterium
- 2. the bacterium is degraded releasing endotoxins to induce macrophage to produce interleukin -1 (IL - 1)
- 3. IL-1 is released into bloodstream to travel to hypothalamus
- 4. IL-1 induces hypothalamus to produce prostaglandins which reset the body's thermostat to a higher temperature producing fever
pathogen associated molecular patterns
conserved microbial molecular structures that are recognized by the host's immune response called pattern recognition receptors
what are some types of PRRs (pattern recognition receptors)
- toll like receptors
- NOD like receptors
what is the effect of endotoxin on immunity?
- cause fever
- acitvate clotting cascade
- complement activation
- increased heart rate
- increased respiration
- induces the release of pyrogens
what is the effects of high levels of endotoxin on the body?
- septic shock
- systemic blood clots
- multi organ failure and death
the immune response to tissue injury due to infection of autoimmune reaction
what are the tissue responses to inflammation?
- vasodilation - capillary diameter increases
- vascular permeability increases
- movement of leukocytes into tissues attracted by chemokines
functions of inflammation
- increased blood flow
- increased temperature
- chemotactic factors
release of inflammatory mediators from injured tissue cells initiates a cascade of events resulting in the signs of inflammation
- slow process (weeks)
- usually causes permanent tissue damage
- involves formation of new connective tissue
- dense infiltration of lymphocytes and macrophages at site of inflammation
- formation on new connective tissue
- formed when phagocytes cannot destroy pathogen
- walled off area
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