Innate immunity Flashcards
immunity
body’s ability to resist disease
innate
non specific
adaptive
acquired and specific
innate resistance to infection
- protect humans from most infectious diseases
- natural host resistance
- infection site and tissue specificity
-protect humans from most infectious disease
- exists at birth and always present
- natural host resistance (no memory)
- can be specific for tissue
- chemical and physical barriers, special immune system cells, physiological processes and molecular defences
natural host resistance
susceptibility to pathogens varies from species to species
-ex anthrax: fatal blood infection in cattles vs cutaneous in humans
infection site and tissue specificity
- pathogens prefer a specific body site to initiate infection
- nutritional and metabolic needs
- eg. colstridium tetani: ingested vs deep wounds
physical and chemical barriers
mucous membranes skin respiratory tract gastrointestinal tract genitourinary tract
genitourinary tract
- urine-metabolic waste products, toxic to many microbes
- flushing action-mechanical removal of mircboes
- normal microbiota
- ex. vaginal epithelial cells produce glycogen
- lactobacillus acidophilus ferments the ferments the flucose to lactice acid
- pH~3-5
gastrointestinal tract
stomach
small intestine
large intsetine
stomach
- strong acidity (pH~2)
- proteolytic enzymes
- destroys most microbes
small intestine
- rapid change in pH
- pancreatic enzymes
- bile
- destroy microbes
large intestine
the normal microbiota
- microbes that already reside in and on the human body
- take up attachement sites
- limit available nutrients
- make antimicrobial compounds
respiratory tract
- the mucocilliary escalator
- ciliated cells line the mucous membranes of the airways
- sweeping action moves mucous and microbes away from the lungs
mucous membranes
- mucous traps microbes
- contains antimicrobial secretions
ex. - lysozyme-cuts B-1,4 glycosidic bonds in peptidoglycan
- defensins-antimicrobial peptides that poke holes in bacterial cell membranes
skin
- prevents invasion by microbes
- protective protein-keratin
- slightly acidic ~pH 5
- high [NaCl]- periodic drying
the lymphatic system
a collection of tissues that bring specialized cells (lymphocytes) into contact with foreign material (antigens)
lymphatic system is made up of
lymphoid organs and lymph vessels that carry fluid (lymph)
- similar to blood containing white blood cells (leukocytes)
- but without red blood cells
lymphoid organs
- primary lymphoid organs
- secondary lymphoid organs
- mucosa associated lymphoid tissue (MALT)
primary lymphoid organs
bone marrow and thymus- leukocytes are produces and mature
secondary associated lymphoid organs
- lymph nodes, spleen, MALT
- contains leukocytes arranged to filter out microbes and antigens
MALT
leukocytes constantly sample their surroundings by phagocytosis looking for foreign material
leukocytes (white blood cells)
- cells that circulate in the blood and lymph, and reside in lymphoid organs
- involved in both branches of the immune response (innate and adaptive)
three types of leukocytes
- granulocytes
- monocytes
- lymphocytes
granulocytes
-cytoplasm contains granules filled with reactive chemicals
-can kill microbes
-signal other components of immunity
3 types:
basophils and mast cells
eosinophils
neutrophils
monocytes
-circulate in the blood and then migrate into tissues and differentiate into macrophages and dendritic cells
-strongly phagocytic cells involved in antigen presentation
2 types:
macrophages
dendritic cells
lymphocytes
-specialized leukocytes involved primarily in the adaptive immune response
-circulate through the blood and reside in lymphoid organs
3 types :
1. B lymphocytes (B cells)
2. T lymphocytes (T cells)
3. Natural Killer cells (NK cells)
basophils and mast cells
- granules stain with basic dyes
- non phagocytic
- circulate in blood (basophils) or reside in mucosal tissue (mast cells)
- can be triggered to degranulate
- release vasoactive mediators
- trigger inflammation
ex. histamine-involved in the allergic response
eosinophils
- granules stain with acidic dyes
- non phagocytic
- can leave the blood and enter tissues in areas of inflammation
- attck large parasites: protozoa and parasitic worms
- release reactive oxygen intermediates:
- O2-, H2O2, OH*
- destroy parasite from the outside
Neutrophils
- granules are filled with digestive enzymes: lysozyme and defensins
- circulate in blood and migrate to infection sites
- highly phagocytic-“eat” invading bacteria
- central component of innate immunity
macrophages
- reside in tissues- lungs, liver, spleen. connective tissues
- specific surface molecules recognize pathogens-Toll-like receptors:
- LPS, peptidoglycan, fungal cell walls etc.
- induces phagocytosis
dendritic cells
- reside in tissues that serve as common entry points for pathogens
- skin- “langerhan’s cells”
- mucous membranes of the nose, lungs and intestines
- constantly sample surroundings by phagocytosis
- migrate to lymphoid organs
- they then present foreign antigens on their surface to B ant T lymphocytes - trigger the specific (adaptive) immune response
B lymphocytes
b cells
- antibody producing cells
- involved in the humoral immune response
T lymphocytes
T cells
-involved in the cell mediated immune response
natural killer cells (NK cells)
-destroy abnormal body cells:
cancer cells
celles infected by bacteria or viruses
leukocytes: recap
granulocytes
basophils/ mast cells
eosinophils
neutrophils
leukocytes: recap
agranulocytes
monocytes
macrophages
dendritic cells
lymphocytes (Band T lymphocytes, NK cells)
innate immunity
-the innate ability to destroy a pathogen that has never been encountered before
innate immunity involves phagocytic leukocytes (neutrophils and macrophages) that recognize…
pathogen-associated molecular patterns (PAMPs)
- lipopolysaccharide
- lipoteichoic acid
- flagellin
phagocytes have …
toll-like receptors (pattern recognition receptors or PRRs)
- interacts with a PAMP
- triggers phagocytosis
- binding by phagocyte PRR activates phagocytosis to kill pathogen
innate response mechanism: phagocytosis
- Phagocytes engulf and destroy invading microbes
- engulfs it into a phagosome
- fuses with a lysosome to form a phgolysosome
phagosomes are filled with
- lysozyme and defensins
- proteases
- lipases
- nuclease
- oxygen independent killing
proteases
degrade proteins
lipases
degrade phospholipids
nuclease
degrade nucleic acids
oxygen independent killing
- activated phagocytes produce reactive oxygen compounds:
- H2O2, O2-, OH,HOCI,NO
- kill ingested microbes by oxidizing cell components
once invaders have been killed by phagocytosis
- neutrophils perform exocytosis
- fragments are expelled from the cell
- macrophages and dendritic cells become antigen presenting cells
- fragments of the cell surface to trigger an adaptive immune response
inflammation
-general, non-specific reaction to pathogens, toxins or tissue damage
five cardinal signs of inflammation
redness warmth pain swelling loss of function
pro-inflammatory cytokines
in response to infection, injured tissue and leukocytes release pro-inflammatory cytokines
- blood vessels dilate
- brings more leukocytes to the area
- vessel walls become permeable
- leukocytes can squeeze into tissues -extravasation
- attack invading pathogens
- temperature increase may slow the growth of pathogens
- blood leaking into tissue spaces can clot
- prevents movement of pathogens
