Innate Host Immunity Flashcards
what 2 things mucst pathogens overcome in order to cause disease?
- must overcome surface barriers and reach underlying tissues
- must overcome resistance by host
what is the first line of defense against disease causing pathogens?
surface barriers of host
what are the 2 aspects of resistance by host?
- nonspecific resistance
2. specific immune response
what is the immune system? Define and give function
- composed of widely distributed cells, tissues, and organs
2. recognizes foreign substances or microbes and acts to neutralize or destroy them
what is immunity?
the ability of the host to resist a particular disease or infeciton
what is immunology?
the science concerned with immune responses
what is the nonspecific immune response also called? (3)
- nonspecific resistance
- innate immunity
- natural immunity
what is the first line of defense of immunity specifically
nonspecific immune response
what does the nonspecific immune response do?
offers resistance to any microbe or foreign material
does the nonspecific immune response have any immunological memory?
no
list 3 other names for the specific immune response
- acquired
- adaptive immunity
- specific immunity
to what does the specific immune response have resistance?
a particular foreign agent
discuss the memory of the specific immune response
has memory! effectiveness increases on repeated exposure to agent
what 2 things are the physical barriers in nonspecific (innate) immunity impacted by?
- direct factors
2. indirect factors
list 5 direct factors that effect the effectiveness of physical barriers in nonspecific (innate) immunity
- nutrition
- physiology
- fever
- age
- genetics
list 3 indirect factors that effect the effectiveness of physical barriers in innate (nonspecific) immunity
- personal hygiene
- socioeconomic status
- living conditions
give an example of personal hygiene as an indirect factor effecting the effectiveness of physical barriers in innate (nonspecific) immunity
feral dogs and cats are in good physical condition, so they are more susceptible to disease
what are the 2 aspects of nonspecific resistance (innate) that are the first line of defense agiant microbes?
- physical barriers
2. host secretions (flushing)
what are the 6 physical barriers in innate (nonspecific) resistance?
- skin
- mucous membranes
- respiratory system
- gastrointestinal tract
- genitourinary tract
- the eye
describe the skin
- a strong mechanical barrier to microbial invasion
2. an inhospitable environment for microbes
what is the skin made of?
keratin produced by keratinocytes in outer layer
list 4 reasons why the skin is an ihospitable environment for microbes
- attached organisms removed by shedding of outer skin cells
- pH is slightly acidic (most microbes no like)
- high NaCl concentration (most microbes no like)
- subject to periodic drying
describe mucous membranes (2)
- form protective covering that resists penetration and traps many microbes
- are often bathed in antimicrobial secretions which contain a variety of antimicrobial substances
list and describe the function of 3 antimicrobial substances found in mucous membranes
- lysozyme: hydrolyzes bonds connecting sugars in peptidoglycan
- lactoferrin: secreted by certain immune cells and sequesters iron (that microbes need for metabolic processes) from plasma and away from microbes
- lactoperoxidase: produces superoxide radicals
list the 3 physical barrier aspects of the respiratory system
- turbulent air flow deposits microbes onto mucosal surfaces
- mucociliary blanket
- alveolar macrophages
describe how the respiratory system uses a mucociliary blanket as a physical barrier against microbes (3)
- mucous secretions trap microbes
- once trapped, microbes are transported away from the lungs on the mucociliary escalator
- the microbes are then expelled by coughing or sneezing or salivation washes microbes into the stomach for death
describe how the alveolar macrophages of the respiratory tract serve as a physical barrier
phagocytic cells in alveoli of lungs eat microbes
what are the 3 aspects of the GI tract that function as physical barriers?
- stomach
- small intestines
- large intestines
how does the stomach function as a physical barrier in the GI tract?
gastric acid
in what 4 ways does the small intestine function as a physical barrier in the GI tract?
- pancreatic enzymes
- bile!!
- intestinal enzymes
- peristalsis
in what 3 ways do the large intestines function as a physical barrier in the GI tract?
- shedding of columnar epithelial cells
- secretory IgA
- normal microbiota (good gut bacteria)
in what 3 ways does the genitourinary tract function as a physical barrier?
- unfavorable environment for foreign microbes
- flushing with urine and mucus
- distance barrier of male urethra
list the 3 ways that the genitourinary tract is an unfavorable environment for foreign microbes
- low pH or urine and vagina
- vagina has lactobacilli
- urea and other toxic metabolites are end products in urine
qhat is the importance of the vagina having lactobacilli in innate immunity?
fetus 1st introduction to microbes usually, so offspring born with vaginal birth have a more robust and diverse initial immunity than C-section offspring
describe the distance barreir of the male urethra to pathogens
it is a long way for microbes to travel with no good environment or nutrients, so most die before they get inside from urethra
give the 3 ways that the eye functions as a physical barrier
- mucus-secreting epithelial membrane
- flushing action of tears
- lysozyme, lactoferrin, and secretory IgA in tears as well
describe chemical mediators in innate (nonspecific) resistance
a variety of defensive chemicals such as defensins and other polypeptides are found in blood, lymph, tears, and other body fluids
where are defensive proteins found?
in the blood
what is the complement system?
composed of over 30 defensive proteins, located in the blood, that augment or complement the antibacterial activity of antibodies
what are the 3 major activities of the complement system?
- defending against bacterial infections
- bridging innate and adaptive immunity
- disposing of wastes
what is opsonization?
the process in which microbes are coated by serum components (called opsonins) in preparation for recognition/ingestion by phagocytic cells
what do some complement proteins function as? describe this function
opsonins; bind to microbial cells, coating them for phagocyte recognition
what are the 3 ways opsonization can occur?
- coat microbe with antibodies
- coat microbe with complement proteins
- coat microbe with antibodies AND complement proteins (big red flag)
list 3 other functions of complement proteins
- function as chemotatic signals that recruit phagocytes to their activation site
- puncture cell membranes causing cell lysis
- many complement activities unite the specific and nonspecific arms of the immune system to destroy and remove invading pathogens
describe complement activation (3 aspects)
- complement proteins are produced in inactive forms
- the complement proteins are activated following enzymatic cleavage
- the complement proteins MUST be activated in a cascade fashion
what are the 3 pathways of complement protein activation?
- alternative
- lectin
- classical
what is the alternative complement pathway involved in?
nonspecific defenses against intravascular invasion by bacteria/fungi
does the alternative complement pathway happen as a result of immune memory?
no, it just happens
what is the alternative complement pathway dependent on?
dependent on interaction of complement with repetitive structures on pathogens
how does the alternative complement pathway begin?
with activation of C3 protein
what are the 2 most common complement proteins?
C3 and C5
what does the alternative complement pathway result in?
formation of the membrane attack complex
describe the membrane attack complex, and give what complement pathway it comes from
forms pores/openings in cell wall leading to a loss in pathogen cell homeostasis and destruction of the cell wall, results from the alternative complement pathway
what is the lectin complement pathway also called?
the mannose-binding lectin pathway
what does the lectin pathway begin with?
activation of C3 and lectin binding
what is the lectin complement pathway dependent on?
dependent on interaction of host mannose-binding protein (MBP) with pathogen surfaces
what does the lectin binding pathway result in?
enhances phagocytosis by burrowing into mannose
what is the classical complement pathway usually dependent on?
usually dependent on antigen-antibody interactions
what kind of immunity is the classical complement pathway part of and what does this mean about its speed?
part of acquired immunity, so it is not as fast as other pathways
what does the classical complement pathway produce?
cleavage products that participate in opsonization, chemotaxis (to attract phagocytes), 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 (basically how cells communicate)
what are the 3 proposed groups of cytokines based on function?
- regulators of innate resistance mechanisms
- regulators of adaptive immunity
- stimulators of hematopoiesis
what is hematopoiesis?
blood immune cell production/differentation
what are the 4 types of cytokines based on function?
- chemokines
- interleukins
- interferons
- colony stimulating factor
describe the function of chemokines
stimulate cell migration
describe the function of interleukins
released from one leukocyte and act on another leukocyte
describe the function of interferons
regulatory cytokines produced in response to infection
describe the function of colony stimulating factors
stimulate growth and differentiation of immature leukocytes in bone marrow
what is one additional class of cytokine and its function?
tumor necrosis factors: stimulate an imflammatory response
list 6 cell types of the immune system
- granulocytes
- mast cells
- monocytes and macrophages
- dendritic cells
- lymphocytes
- leukocytes
where are mast cells dderived?
from bone marrow
where do mast cells differentiate?
in blood and connective tissue
what do mast cells contain?
granules containing histamine and other pharmacologically active chemicals
what do mast cells play an important role in?
development of allergies and hypersensitivities, and vasodilation
describe how mast cells play a role in vasodilation and what this does
release of their chemicals opens blood vessels, and more blood to the site allows other immune blood cells to come and help in response
describe granulocytes (looks)
irregularly shaped nuclei with two to five lobes
what is in the cytoplasm of granulocytes?
granuals with reactive substances that kill microbes and enhance inflammation
what are the 3/4 types of granulocytes?
- basophils
- eosinophils
- neutrophils
(4) polymorphonuclear neutrophil
describe the main function of neutrophils
highly phagocytic
how do neutrophils do all that phagocytosis?
circulate in blood then migrate to sites of tissue damage, where they kill ingested microbes with lytic enzymes and reactive oxygen metabolites contained in primary and secondary granules
what is the byproduct of neutrophils’ cosumption of microbes and subsequent apoptosis?
pus formation
what are 2 other cells that are highly phagocytic besides neutrophils?
monocytes and macrophages
what are monocytes?
immature macrophages; mononuclear phagocytic leukocytes
how do monocytes mature into macrophages?
after circulating for about 8 hours in the blood, they migrate to tissues and mature into macrophages
describe macrophages
larger than monocytes and reside in specific tissues
how are macrophages named?
according to the tisse in which they reside
what do macrophages have to aid in their function?
a variety of surface receptors, including pattern recognition receptors that bind pathogens/microbe associated molecular patterns (PAMPs)
where are dendritic cells?
heterogeneous group of cells with neuron-like appendages
where are dendritic cells found?
in small numbers in the blood, skin, and mucous membranes of nose, lungs, and intestines
what do dendritic cells do that is similar to macrophages?
also express pattern recognition receptors
describe the function of macrophages
contact, phagocytose, and process antigens, then display those foreign antigens on their surfaces (antigen presentation)
describe lymphocytes
majore cells of the adaptive immune system
what do lymphocytes include? (3)
T cells, B cells, and Natural Killer (NK) cells
where do T and B lymphocytes differentiate? from what?
in bone marrow from stem cells
what are T and B cells activated by?
binding of specific antigen onto lymphocute surface receptors
what happens to T and B cells after activation?
replication continues as lymphocytes circulate and enter lymphoid tissue
what are memory cells?
activated lymphocytes that do not immediately replicate, but will do so later in the host’s life when the antigen is again present
where do B lymphocytes mature?
in Bone marrow
where do B lymphocytes circulate?
in blood
where can B lymphocytes settle?
in lymphoid organs
what are B lymphocytes called after maturation? what do they produce?
plasma cells; produce antibodies
where do T cells mature?
the Thymus
where are mature T cells found? (3)
- can remain in Thymus
- can circulate in blood
- can reside in lymphoid tissue
what do T cells require for activation and continuation of replication (like B cells)
antigen binding
what 2 types do T cells differentiate into once activated?
- helper T cells (TH)
2. cytotoxic lymphocytes (CTLs)
what do T cells do?
secrete and activate cytokines, which are chemicals that have effects on other cells
what occurs in the primary organs and tissues of the immune system?
sites where lymphocytes mature and differentiate into antigen-sensitive mature B and T cells
what occurs in the secondary organs and tissues of the immune system?
areas where lymphocytes may encounter and bind antigen; followed by proliferation and differentiation into fully mature effector cells
what are the 2 primary organs/tissues of the immune system?
- Thymus
2. bone marrow
describe what happens in the thymus, a primary organ of the immune system (4)
- precursor cells move from bone marrow and proliferate
- thymic deletion removes T cells’ self-recognizing antigens
- remaining celsles become mature T cells
- the mature T cells enter the blood stream and recognize NONself antigens
describe the bone marrow as a primary organ/tissue of the immune system
site of B cell maturation in MAMMALS
what does B cell maturation in Bone marrow involve?
removal of nonfunctioig and self-reactive cells
describe lymph nodes as a secondary organ/tissue of the immune system
most highly organized lymphoid tissue
what do lymph nodes do?
fiilter lymph
describe the 2 mechanisms/hardware of lymph nodes to filter lymph
- microbes and antigens are trapped and phagoctyosed by macrophages and dendritic cells
- B cells differentiate into memory and plasma cells within lynph nodes
what do plasma B cells do?
help destroy pathogens
give 2 other secondary tissues/organs of the immune system other than lymph nodes
- spleen
2. lymphoid tissue (skin and mucous associated)
what is phagocytosis?
the process by which pahgocytic cells, such as monocytes, tissue macrophages, dendritic cells, and neutrophils, recognize, ingest, and kill extracellular microbes
what are the 2 mechanisms for microbe recognition by phagocytes?
- opsonin-independent (nonopsonic) recognition
2. opsonin-dependent (opsonic) recognition
what can greatly increase phagocytosis?
opsonization
describe opsonin-DEpendent phagocyte pathogen recognition
phagocytes recognize serum proteins attached to pathogens (the big red flag to attract help)
describe opsonin-INdependent phagocyte pathogen recognition (2)
- common pathogen components are non-specifically recognized to activate phagocytosis, with signalling mechanism now involved
- involved nonspecific/specific receptors on phagocytes
describe opsonin INdependent phagocyte pathogen recognition, VERY generally
body can still find pathogens, it just may take longer to find them and recruit helpers for the immune attack
describe intracellular digestion of microbes
once bound, microbes can be internalized and delivered to a lysosome to become a phagolysosome
what occurs once a lysossome becomes a phagolysosome?
respiratory burst reactions occur
what does a phagolysosome produce and what does this do?
produces toxic products like hydrogen peroxide which can kill invading microbes
why is antigen presentation an important process?
because it allows wandering lymphocytes to become activated
what does antigen presentation link?
specific and nonspecific immune responses
what is inflammation? what can it be caused by?
nonspecific response to tissue injury, can be caused by pathogens or physical trauma
what is the immediate response of the body to injury or cell death?
acute inflammation
what are the 5 cardinal signs of inflammation?
- redness (rubor)
- warmth (calor)
- pain (dolor)
- swelling (tumor)
- altered function (functio laesa)
describe acute inflammation
the release of inflammatory mediators from injured tissue cells initiates a cascade of events which result in the 5 cardinal signs of imflammation
what are the 4 chemical mediators involved in acute inflammation?
- selectins
- integrins
- chemotaxins
- kallikreins
what are selectins in acute inflammation? what do they do?
cell adhesion molecules on activated capillary endothelial cells, slow down circulating neutrophils to keep in needed areas
what are integrins in acute inflammation?
adhesion receptors on neutrophils
what are chemotaxins in acute inflammation? what do they do?
chemotactic factors released by injured cells, recruit immune cells to the area and trigger responses
what are kallikreins in acute inflammation?
enzymes that loosen tight junctions, involved in pain response
what 2 processes occur in acute inflammation?
- margination
2. diapedesis/extravasion
what do mast cells do in the acute inflammatory response?
release histamines to help with dilation to increase blood flow and loosen tight junctions to allow neutrophils into affected area
