Innate Immunity Flashcards
what must most pathogens do?
overcome surface barriers and reach underlying tissues
overcome resistance by host
how do pathogens overcome resistance by hosts?
nonspecific resistance
specific immune response
what is the immune system?
composed of widely distributed cells, tissues, and organs
recognizes foreign substance or microbes and acts to neutralize or destroy them
what is immunity?
ability of host to resist a particular disease or infection
what is immunology?
science concerned with immune response
what is the nonspecific immune response?
innate or natural immunity
acts as first line of defense
offers resistance o any microbe or foreign material
lacks immunological memory
what is the specific immune response?
acquired or adaptive immunity
resistance to particular foreign agents
has memory
effectiveness increases on repeated exposure to agent
what is the effectiveness of physical barriers impacted by in innate resistance?
direct factors and indirect factors
what are examples of direct factors?
nutrition, physiology, fever, age, and genetics
what are examples of indirect factors?
personal hygiene, socioeconomic status, and living conditions
what is the first defense against microbes?
barriers and host secretions
skin as a barrier
strong mechanical barrier to microbial invasion due to the keratin produced in the outer layer
inhospitable environment for microbes because:
attached organisms removed by shedding of outer skin cells
pH is slightly acidic
high NaCl concentration
subject to periodic drying
what do the mucous membranes do?
form protective covering that resists penetration and traps many microbes
are often bathed in antimicrobial secretions which contain a variety of antimicrobial substances
what are the three types of antimicrobial secretions?
lysozyme- hydrolyzes bond connecting sugars in peptidoglycan
lactoferrin- secreted by certain immune cells and sequesters iron from plasma
lactoperoxidase- produces superoxide radicals
how does the respiratory system protect against microbes?
turbulent air flow deposits microbes onto mucosal surfaces
mucociliary blanket
alveolar macrophages
what does the mucociliary blanket do?
mucus secretions trap microbes
once trapped, microbes are transported away from the lungs and are expelled by coughing, sneezing, or salivation washing it into the stomach
how does the stomach protect against microbes?
stomach acid
how do the small intestines work against microbes?
pancreatic enzymes
bile
intestinal enzymes
peristalsis
how do the large intestines work against microbes?
shedding of columnar epithelial cells
secretory IgA
normal microbiota
why is the genitourinary tract and unfavorable environment for foreign microbes?
low pH of urine and vagina
vagina has lactobacilli
urea and other toxic metabolic end products in urine
has flushing via urine and mucus
there is a distance barrier in the male urethra
what protections does the eye offer against microbes?
flushing action of tears
mucus secreted by the epithelial membrane
lysozyme, lactoferrin, and secretory IgA in tears
what are the chemical mediators in the innate immune response?
variety of defensive chemicals such as defensives and other polypeptides found in the lymph, blood, and other body fluids
defensive proteins are found in the blood
complement characteristics
composed of over 30 serum proteins
augments the antibacterial activity of the antibody
has three major activities
what are the three major activities of complement?
stimulates an inflammatory response by helping to recruit white blood cells
lysing microbial cells
promoting phagocytosis through opsonization
what is opsonization?
process in which microbes are coated by serum components in preparation for the recognition/ingestion by phagocytic cells
what are some other functions of complement proteins?
function as chemotactic signals that recruit phagocytes to their activation site
puncture cell membranes causing cell lysis
many complement activities unite the innate immune system and adaptive arms of the immune system to destroy and remove invading pathogens
how does complement activation take place?
produced in inactive forms
activated following enzymatic cleavage
must be activated in cascade function
take place in one of three pathways
what are the three pathways of complement activation?
alternative
lectin
classical
what are the major differences between pathways?
the types of molecules that activate each pathway
the means by which key proteases are activated
the identity of the proteases
what are the characteristics of the alternative pathway?
involved in nonspecific defenses against intravascular invasion by bacteria/fungi
dependent of the interaction of complement with repetitive structures on pathogens such as LPS and techie acids
what are the characteristics of the alternative pathway?
involved in nonspecific defenses against intravascular invasion by bacteria/fungi
dependent of the interaction of complement with repetitive structures on pathogens such as LPS and techoic acids
begins with activation of C3
results in formation of the membrane attack complex
characteristics of the lectin pathway
also called the mannose-binding lectin pathway
begins with activation of C3 and lectin binding
dependent on interaction of host mannose-binding protein with pathogen surfaces to enhance phagocytosis
characteristics of the classical pathway
produces cleavage products that participate in opsonization, chemotaxis, and the membrane attack complex
what are cytokines?
soluble proteins or glycoproteins that are released by one cell population that act as intracellular mediators or signaling molecules
hat are the three simplified categories of cytokines?
regulators of innate immunity
regulators of adaptive immunity
stimulators of hematopoiesis
what are the four functional groups of cytokines?
chemokines
interleukins
interferons
colony stimulating factors
additional: tumor necrosis factor
what do chemokines do?
stimulate cell migration
what do interleukins do?
released from one leukocyte and act on another leukocyte
what are interferons?
regulatory cytokines produced in response to infection
what are colony stimulating factors?
stimulate growth and differentiation of immature leukocytes in bone marrow
what does the tumor necrosis factor family do?
stimulate an immune response
what are the 6 types of immune cells?
granulocytes
mast cells
monocytes and macrophages
dendritic cells
lymphocytes
leukocytes
leukocyte characteristics
white blood cels
involved in both specific and nonspecific immunity
all arise from pluripotent stem cells
mast cell characteristics
bone-marrow derived cells
differentiate in blood and connective tissue
contain granules contain vasoactive mediators such as histamines
play important role in the development of allergies and hypersensitivities
granulocyte characteristics
irregularly shaped nuclei with two to five lobes
cytoplasm has granules with reactive substances that kill microbes and enhance inflammation
what are the three types of granulocytes?
basophils
eosinophils
neutrophils
neutrophil characterisitcs
highly phagocytic
circulate in blood then migrate to sites of tissue damage
kill ingested microbes with lytic enzymes and reactive oxygen metabolites contained in primary and secondary granules
monocyte characteristics
produced in bone marrow and release into blood circulation
after circulating for 8 hours, mature into macrophages
macrophage characteristics
larger than monocytes, reside in specific tissues, highly phagocytic
release chemokines to recruit neutrophils
dendritic cell characterisitcs
many long cellular projections
present in blood, skin, and mucous membranes of the nose, lungs, and intestines
contact, phagocytose, and process antigens before displaying the antigen on their surfaces
capable of eliciting immune response for T-cells, activating the adaptive immune system
lymphocyte characteristics
major cells of the adaptive immune system
T cells, B cells, NK cells
have innate immune function trough innate lymphoid cells
innate lymphoid cell characteristics
NK cells
do not have memory
stimulated same methods as neutrophils, macrophages, and DC
what is phagocytosis?
process by which phagocytic cells recognize, ingest, and kill extracellular microbes
can be greatly increased by opsonization
two mechanisms of recognition
what are the two mechanisms of recognition for phagocytosis?
opsonin-dependent and opsonin-independent
how does the opsonin dependent mechanism work?
recognizes serum components attached to pathogens
how does the opsonin independent mechanism work?
common pathogen components are non-specifically recognized to activate phagocytes- signaling mechanism involved
involves nonspecific/specific receptors on phagocytes
how does intracellular digestion work?
once bound, microbes can be internalized and delivered to a lysosome to become a phagolysosome
respiratory burst reactions occur once the phagolysosome forms
toxic oxygen products are produced which can kill invading microbes
what is inflammation?
nonspecific response to tissue injury
can be caused by pathogen or physical trauma
acute inflammation is the immediate response of body to injury or cell death
what are the cardinal signs of inflammation?
redness
warmth
pain
swelling
altered function
what is the acute inflammatory response?
the release of inflammatory mediators from injured tissue cells initiates a cascade of event which result in the signs of inflammation
involves chemical mediators such as selecting, interns, and chemotaxins
what are selectins?
cell adhesion molecules on activated capillary endothelial cells
what are integrins?
adhesion receptors on neutrophils
what are chemotaxins?
chemotactic factors released by injured cells
what occurs during an acute inflammatory response?
capillaries widen to increase blood flow
increased permeability of vessels causes fluid release into the tissues
attraction of leukocytes to the site of injury
a systemic response through fever and proliferation of leukocytes
