Lesson 12a - Lymphoid and Immune System Flashcards
pathogens
agents capable of producing disease, including viruses, bacteria, fungi, and other microbes
three lines of defenses: first line of defense
skin and mucous membranes, which serve as barriers
three lines of defenses: second line of defense
protects against pathogens that break the skin and mucous membrane barriers
the second line of defense includes (7)
- leukocytes
- macrophages
- antimicrobial proteins
- natural killer cells
- fever
- inflammation
three lines of defenses: third line of defense
adaptive immunity, mechanisms that defeat a specific pathogen and leave the body with a memory of it
immune system
widely distributed population of cells, diverse chemicals, physical barriers, and physiological responses
two broad forms of defense
- innate immunity
- adaptive immunity
innate immunity
defenses we are born with that protect us from broad spectrum of disease agents
innate immunity has…(3)
- local effect
- non-specific
- lacks memory
innate immunity: local effect
defends at point of invasion, but there are exceptions like fever
innate immunity: non-specific
defenses are against a broad spectrum of disease agents, rather than on particular pathogen
innate immunity: lacks memory
does not ‘remember’ exposure to a specific pathogen
adaptive immunity
defenses against specific pathogens, developed only upon exposure (adaptive) and maintains immune memory
peptides in the skin that kill microbes (3)
- dermcidin
- defensins
- cathelicidins
protective features of skin (4)
- toughness of keratin, difficult to penetrate
- too dry/nutrient-poor to support microbial growth
- skin is continually shed so microbes ‘don’t stick’
- presence of an acid mantle
acid mantle
thin film of lactic and fatty acids from sweat and sebum that inhibits bacterial growth
digestive, respiratory, urinary, and reproductive tracts are open to the exterior and protected by _____ _____
mucous membranes
protective features of mucous membranes (2)
- sticky mucous physically traps microbes
- presence of lysozyme
lysozyme
enzyme that destroys bacterial cell walls
protective features of subepithelial areolar tissue of skin and mucous membranes
contain a viscous barrier of hyaluronic acid in ground substance
pathogens can release _____
hyaluronidase
hyaluronidase
an enzyme to make hyaluronic acid less viscous
phagocytes
cells that engulf foreign matter
five types of leukocytes
- neutrophils
- eosinophils
- basophils
- monocytes
- lymphocytes
where are neutrophils found?
wander in connective tissue and functions to kill bacteria
neutrophils can ensnare bacteria by releasing…
a neutrophil extracellular trap (NET)
neutrophil extracellular trap
web of nuclear chromatin and proteins
neutrophils can kill by… (2)
- phagocytizing and digesting microbe
- releasing bacterial chemicals to create a killing zone
where are eosinophils found?
especially in mucous membranes
what do eosinophils guard against?
large parasites like tapeworms, and roundworms
eosinophils also participate in…(2)
- participate in inflammation
- react to allergens and participate in allergic reactions
basophils
secrete chemicals that aid mobility and action of other leukocytes
leukotrienes
activate and attract neutrophils and eosinophils
histamine
a vasodilator; increases blood flow and speeds delivery of leukocytes to the area
heprin
inhibits clot formation that would impede leukocyte mobility
mast cells
also secrete these substances; similar to basophils but found in connective tissues
lymphocytes include…
T and B cells, and also Natural Killer cells
T and B cells are part of innate/adaptive immunity?
adaptive
Natural killer (NK) cells are part of the innate/adaptive immunity?
innate
monocytes
emigrate from the blood into connective tissues and transform into macrophages
macrophage system
all the body’s avidly phagocytic cells, expect leukocytes
- includes monocytes, macrophages, dendritic cells, and others
specialized macrophages in the CNS, lungs, and liver
- microglia: CNS
- alveolar macrophages: lungs
- stellate macrophages: liver
interferons
proteins secreted by virally infected cells and immune cells to serve as an alarm to nearby cells
what do interferons do? (2)
- bind to receptors on nearby cells, stimulating their synthesis of defensive antiviral proteins to prevent their infection
- activate NK cells and macrophages to better destroy infected cells/cancer cells
complement system
group of 30 or more globular proteins that contribute to both innate and adaptive immunity
what synthesizes most of the complement system?
the liver
T/F the complement system circulated in the blood in an inactive form
true
what complement contributes to inflammation
C3a
what complement contributes to immune clearance, phagocytosis, and cytolysis?
C3b
three complement pathways
- classical
- alternative
- lectin
classical pathway
requires antibody binding to microbe, which changes the antibody’s shape and exposes complement-binding sites on the antibody
complement fixation
binding of the complement C1 to the antibody sets of a reaction cascade
alternative pathway
complement Cb3 binds to microbe surface, activating reaction cascade
lectin pathway
use lectins to trigger the pathwaysl
lectins
plasma proteins that bind to carbohydrates on the pathogen’s surface, activating reaction cascade
four outcomes of complement activation
- inflammation
- immune clearance
- phagocytosis
- cytolysis
outcomes of complement activation: phagocytosis
C3b coats microbial cells and serves as binding sites for phagocyte attachment
opsonization
proteins coat microbial cells that serve as binding sites for phagocyte attachment
outcomes of complement activation: inflammation
C3a stimulates mast cells and basophils to secrete histamine and other inflammatory chemicals which activates and attracts neutrophils and macrophages
outcomes of complement activation: immune clearance
C3b binds the antigen-antibody complexes to red blood cells that then circulate to the liver and spleen where macrophages strip off and destroy the Ag-Ab complexes leaving the RBCs unharmed
outcomes of complement activation: cytolysis
- complement C3b initiated formation of C5b
- C5b aggregates with other complement proteins within plasma membrane of microbe which forms the membrane attack complex (MAC)
membrane attack complex (MAC)
forms a hole in the target cell membrane, made of complement proteins
process of a MAC on its target cell
electrolytes leak out, water flows rapidly in, and the target cell ruptures (cytolysis)
immunological surveillance
natural killer (NK) cells continually patrol the body looking for pathogens and diseased host cells
NK cells attack and destroy…(4)
- microbes
- transplanted cells
- cells infected with viruses
- cancer cells
NK cells recognize an infected cell and bind to it, releasing proteins called _____
perforins
perforins
polymerize to form a ring to create a hole in the target’s plasma membrane
granzymes
a group of protein-degrading enzymes
process of granzymes
enzymes enter through the pore created by perforins and degrade intracellular enzymes and induce apoptosis
cancer cells may exhibit _____-_____ antigens
tumor-specific
where are tumor specific antigens found?
cell’s plasma membrane
T/F tumor-specific antigens are identified as abnormal by NK cells
true
immunological escape
some cancer cells avoid NK cells
- either destroy NK cells that detect them or avoid detection by not displaying tumor specific antigens or masking them
cells infected with viruses present…
abnormal proteins on their plasma membranes, allowing NK cells to identify and destroy them
fever (pyrexia)
an abnormal elevation of body temperature
fever results from…(5)
- trauma
- infections
- drug reactions
- brain tumors
- other causes
a fever is a defense mechanism that, in moderation, does more good than harm by…(3)
promotes…elevates…inhibits…
- promotes interferon activity
- elevates metabolic rate and accelerates tissue repair
- inhibits reproduction of bacteria viruses
antipyretics
fever-reducing medications
stages of fever (3)
onset, stadium, defervescence
the body’s thermostat is located in the _____
hypothalamus
Reye syndrome
serious disorder in children younger than 15 following an acute viral infection like chickenpox or influenza
what can Reye syndrome be triggered by?
the use of aspirin, so do not give to children with chickenpox or flu-like symptoms
Reye syndrome symptoms (3)
- swelling of the brain neurons
- pressure of the swelling leads to nausea, vomiting, disorientation, seizures, and coma
- fatty infiltration of liver and other viscera
TLDR; swelling of the liver and brain
inflammation
local defensive response to tissue injury, including trauma and infection
general purposes of inflammation (2)
- limit spread of pathogens and destroys them
- remove debris from damaged tissue and initiate tissue repair
four cardinal signs/symptoms
redness, swelling, heat, pain
cytokines
small proteins that function in chemical communication between cells
what do cytokines do?
alter physiology of receiving cells
cytokines include…(4)
- interferon
- interleukins
- tumor necrosis factor
- chemotactic factors
etc.
what is the most immediate requirement after tissue injury?
to get defensive leukocytes to the site quickly
getting leukocytes to tissue injury sites is achieved by…
local hyperemia (increasing blood flow)
what does hyperemia wash away from injury sites faster? (2)
toxins and metabolic wastes
vasoactive chemicals (2)
- histamine
- leukotrienes
vasoactive chemicals stimulate…(2)
(1) endothelial cells to contract, (2) widening the gaps between them to increase capillary permeability
cell-adhesion molecules aid in..
recruitment of leukocytes
margination
cell-adhesion molecules make membranes sticky, so leukocytes adhere to the vessel wall
diapedesis
emigration
- leukocytes crawl through gasps in the endothelial cells and enter tissue fluid
extravasated
term for cells and chemicals that have left the bloodstream
four cardinal signs of inflammation: heat results from…
hyperemia
four cardinal signs of inflammation: redness results from (2)
hyperemia and extravasated RBCs in tissue
four cardinal signs of inflammation: swelling results from
an increased fluid filtration from the capillaries
four cardinal signs of inflammation: pain results from…(5)
- direct injury to the nerves
- pressure on nerves from edema
- stimulation of pain receptors by prostaglandins
- bacterial toxins
- bradykinin
another priority of inflammation is to prevent _____ from spreading throughout the body
pathogens
_____ filters into tissue fluid and clots to form a sticky mesh that walls off microbes
fibrinogen
_____ prevents clotting at the site of injury
heparin
after leaving the bloodstream, neutrophils exhibit chemotaxis, meaning…
they exhibit attraction to chemicals that guide them to the injury site
respiratory burst
neutrophils absorb O2 to form H2O and release hypochlorite - al highly toxic and creates a killing zone around the cell
neutrophils secrete cytokines for recruitment of _____ and additional _____
macrophages, neutrophils
macrophages and T cells secrete _____-_____ factor to stimulate _____
colony-stimulation, leukopoiesis
neutrophilia
5,000cells/uL to 25,000 cells/uL in bacterial infection
eosinophilia
elevated eosinophil count in allergy or parasitic infection
tissue cleanup and repair primarily involves _____
monocytes
when do monocytes arrive to tissue injurys?
8-12 hours
how does edema contribute to tissue cleanup? (2)
- swelling compresses veins and reduces venous drainage
- forces open valves of lymphatic capillaries, promoting lymphatic drainage of bacteria, dead cells, and debris
pus
yellow accumulation of dead neutrophils, bacteria, cellular debris, and tissue fluid
abscess
accumulation of pus in a tissue cavity
platelet-derived growth factor
stimulates fibroblasts to multiply and synthesize collagen
this is secreted by blood platelets and endothelial cells in injured areas
platelet-derived growth factor
_____ clot forms a scaffold for tissue reconstruction
firbrin
what does pain cause us to do with injuries?
makes us limit the use of a body part so it has a chance to rest and heal
increased heart rate increases…(2)
- metabolic rate
- speeds up mitosis and tissue repair
third line of defense is…
adaptive immunity
three characteristics of adaptive immunity
- it has a systemic effect
- it exhibits specificity
- it has memory
three characteristics of adaptive immunity: systemic effect
act throughout the whole body
three characteristics of adaptive immunity: specificity
generates protection and immunity to specific pathogens on an individual basis
three characteristics of adaptive immunity: memory
when re-exposed to the same pathogen, the body reacts so quickly that there is no noticeable illness
two types of adaptive immunity
- cellular (cell-mediated)
- humoral (antibody-mediated)
cellular (cell-mediated) immunity (2)
- T cells directly attack and destroy foreign cells or diseased cells
- rids body of pathogens that reside inside human cells where they are inaccessible to antibodies
humoral (antibody-mediated) immunity
- B cells become plasma cells that release antibodies that do not directly destroy a pathogen but tag it for destruction
humoral immunity is effective against…(5)
- viruses
- bacteria
- yeasts
- protozoans
- molecular disease agents like toxins, venoms, allergens
natural active immunity
production of one’s own antibodies or T cells as a result of infection or natural exposure to antigen
artificial active immunity
production of one’s own antibodies or T cells as a result of vaccination against disease
vaccine
consists of dead or attenuated (weakened) pathogens that stimulate the immune response without causing the disease
_____ _____ may be given to re-stimulate immune memory to maintain a high level of protection
booster shots
natural passive immunity
temporary immunity that results from antibodies produced by another person (mother to fetus)
how to a fetus and a baby acquire antibodies from their mother? (2)
- fetus is through the placenta
- baby is through breast-feeding
artificial passive immunity
temporary immunity that results from the injection of immune serum (antibodies) from another person or animal
what is the emergency treatment for things like snake bites, botulism, tetanus, and rabies?
artificial passive immunity- injection of immune serum (antibodies) from another person or animal
antigen (Ag)
any molecule that can bind an antibody
most antigens have _____ molecular weight
large, over 10,000 amu
antigens include…(4)
proteins, polysaccharides, glycoproteins, glycolipids
characteristics of antigens (Ag) enable the body to do what?
distinguish self from non-self
epitopes (antigenic determinants)
certain regions of an antigen molecule that stimulate immune responses
haptens (incomplete antigens)
too small to be antigenic in themselves
how may haptens trigger an immune response?
combining with a host molecule creating a complex that the body recognizes as foreign
examples of epitopes (6)
- cosmetics
- detergents
- industrial chemicals
- poison ivy
- animal dander
- penicillin
antibodies (Abs)/immunoglobulins (Igs)
defensive proteins that play a variety of defensive roles
about how many antibodies is the human immune system capable of creating?
roughly 1 trillion different antibodies
where are some antibodies/immunoglobulins found?
membranes of immune cells
soluble antibodes
antibodies dissolved in blood plasma, tissue fluids, lymph, mucus, saliva, intestinal secretions, tears, and breast milk
antibody monomer
basic structural unit of an antibody
antibody structure
four polypeptide chains linked by disulfide bonds
all four chains of an antibody have a _____ region that gives the antibody its uniqueness
variable (V)
antibodies have two larger _____ chains and two _____ chains about half as long
heavy, light
antigen-binding site (2)
(1) formed from the V regions of the heavy and light chains of each arm, (2) attaches to the epitope of an antigen molecule
constant (C) region
has the same amino acid sequence within a given antibody and determines mechanism of antibody action
five antibody classes
- IgA
- IgD
- IgE
- IgG
- IgM
which Ig forms a dimer in places like mucus, saliva, tears, breast milk, and intestinal secretions?
IgA
which Ig is found as a pentamer in plasma and lymph?
IgM
which Ig is a B cell transmembrane anitgen receptor?
IgD
which Ig is bound to receptors on basophils and mast cells?
IgE
which Ig constitutes 80% of circulating antibodies?
IgG
IgA (2)
- prevents pathogen adherence to epithelia and penetrating underlying tissue
- provides passive immunity to newborns
IgD
functions in B cell activation by antigens
IgE (2)
- stimulates release of histamine and other chemical mediators of inflammation and allergy
- stimulates eosinophil defensive actions against parasites
IgG (2)
- predominant antibody in secondary immune response
- capable of complement fixation, can cross placenta to fetus
IgM (2)
- predominant antibody in primary immune response
- strong agglutinating and complement-fixing abilities
what are the lymphocytes of the innate immune system?
natural killer cells (NK)
what are the lymphocytes of the adaptive immune system?
T and B cells
where are T cells produced? where do they migrate?
bone marrow and migrate to the thymus to mature
what happens to T cells in the thymus?
they are tested
positive selection
cortical epithelial cells test developing T cells to ensure they have the proper receptors (no self antigens)
what happens to T cells if they do not have the proper receptors? (aka they react to a self antigen)
they DIE
the immune system is self-tolerant, meaning…
it will not attack one’s own tissue
anergy
self-reactive T cells remain but are unresponsive
with proper receptors, T cell are now _____
immunocompetent
immunocompetent
capable of recognizing antigens presented to them
immunocompetent, unactivated T cells are part of the….
naive lymphocyte pool
where do B cells develop?
bone marrow
B cells that react to self-antigens under either _____ or _____ _____, same as T cell selection
anergy, clonal deletion (death)
when B cells leave the bone marrow, what do they do?
they colonize the same lymphoid tissues and organs as T cells
Self-tolerant B cells do what? (2)
- synthesize antigen surface receptors
- divide rapidly to produce immunocompetent clones
T cells can only recognize antigens presented by…
antigen-presenting cells (APCs)
APCs include (3)
dendritic cells, macrophages, and B cells
the function of APCs depends on…(2)
(1) MHC proteins (2) encoded by major histocompatibility (MHC) complex genes
MHC molecules act as..
identification tags that label every cell of your body as belonging to you
MHC molecules are unique for each individual except for…
identical twins
where are MHC molecules displayed? and with what?
surface of APCs along with a fragment of presented antigen
antigen processing (5)
(1) APC encounters antigen, (2) internalizes it by endocytosis, (3) digests it into fragments, (4) and attaches it to the MHC protein (5) and display it on the plasma membrane
what happens if a T cell encounters an APC with self antigens presented?
it ignores it
what happens when a T cell encounters an APC with a non-self antigen presented?
the appropriate T cell will initiate an immune response against the source of that antigen
APCs and lymphocytes communicate with cytokines called…
interleukins
three classes of T cells
- cytotoxic
- helper
- memory
cytotoxic T cells
carry out attack
helper T cells
promote activities of other immune cells
memory T cells
responsible for memory in cellular immunity
what happens after an APC encounters an antigen? (3)
it (1) processes it, (2) migrates to the nearest lymph node, (3) and displays it to the T cells
T cells respond to two classes of MHC proteins
MHC-I and MHC-II
where do MHC-I proteins occur?
on all nucleated cells
what kind of peptides do MHC-I molecules present?
internal peptides including virus infected cells, and cancer cells
where do MHC-II proteins occur?
only on antigen-presenting cells
what kind of peptides do MHC-II molecules present?
external (phagocytosed, foreign) antigens
MHC restriction (2)
(1) cytotoxic T cells respond only to MHC-I proteins and (2) helper T cells only respond to MHC-II proteins
when does Tc and Th cell activation begin?
when they bind an MHC protein displaying an epitope that the cell is programmed to recognize
costimulation
additional signaling process required for T cell activation
in addition to MHC and antigen binding, T cells must also bind..
signaling proteins on surface of APCs in damaged, infected tissues
what does costimulation help ensure?
the immune system does not launch an attack in the absence of an enemy or else it would turn against one’s own body and injure our tissues (autoimmune disorders)
successful costimulation will trigger _____ _____
clonal selection
clonal selection (3)
(1) activated T cells undergo repeated mitosis to (2) produce identical clones programmed against the same epitope that (3) become either cytotoxic, memory, or helper T cells
Immune memory follows the _____ response in cellular immunity
primary
T cell recall response
since memory cells are long-lived, more numerous than naive T cells, and have fewer steps to be activated, so they respond more rapidly
helper T cells play a central role in coordinating…(2)
both cellular and humoral immunity
when helper T cells recognize the Ag-MHC (MHC-II) complex, what happens?
it secretes interleukins that exert effects
three effects of the interleukins secreted by activated helper T cells (4)
- attract neutrophils, NK cells, and macrophages
- stimulate their phagocytic activity
- inhibit them from leaving the area
- stimulate T and B cell mitosis and maturation
what are the only cells that directly attack other cells?
cytotoxic T cells
when a Tc cell recognizes a complex of Ag-MHC protein on a diseased or foreign cell, it ___ on that cell
docks
what happens after a Tc cell docks onto a diseased cell?
it delivers a lethal hit of chemicals
the cytotoxic T cell lethal hit includes…(4)
perforins, granzymes, interferons, and tumor necrosis factor (TNF)
lethal hit: perforin and granzymes
kills cells in the same manner as NK cells
lethal hit: interferons (2)
inhibit viral replication, recruit and activate macrophages
lethal hit: tumor necrosis factor (TNF)
aids macrophage activation and kills cancer cells
after the lethal hit, what do cytotoxic T cells do?
goes off in search of another enemy cell while the chemicals do their work
immunocompetent B cells have _____ of surface receptors for _____ antigen
thousands, one
what happens when antigens bind to B cell receptors?
(1) it binds several of these receptors, (2) links them together, and (3) then the B cell takes it into itself by receptor-mediated endocytosis
after a B cell endocytosis an antigen, what happens?
processes the antigen and displays fragments onto MHC-II on its surface
helper T cells bind to displayed _____ on B cells and secretes _____ that activate the B cell
antigen-MHC, interleukins
B cell clonal selection gives rise to…
clones of identical B cells programmed against the same antigen
most B cells differentiate into…
plasma cells
some B cells become…
memory B cells (they remember the antigen)
antibodies travel through the body in…(2)
(1) blood and (2) other body fluids
first exposure to an antigen triggers production of what Igs? and how?
(1) IgM and a (2) slower production of IgG
later exposure to an already known antigen produces what Ig?
IgG much more rapidly than the first exposure
antibodies assist in the immune response in four ways
- neutralization
- complement fixation
- agglutination
- precipitation
antibodies: neutralization
masking active regions of an antigen (toxin, virus, microbial cells)
antibodies: complement fixation
activating complement by the classical pathway
antibodies: agglutinaiton
clumping of enemy cells, immobilizing them; having the clump cleared by phagocytosis
antibodies: precipitation
antigen molecules (no whole cells) are clumped by antibodies; clumps cleared by phagocytes
primary response
immune reaction brought about by the first exposure to an antigen
why is the appearance of protective antibodies delayed for 3-6 days?
naive B cells multiple and differentiate into plasma cells
as plasma cells produce antibodies, the _____ _____ rises
antibody titer
antibody titer
level of antibodies in blood plasma
when do IgM levels peak in a primary response?
10 days, soon decline
when does the IgG titer drop to low levels from a primary response?
within a month
secondary (anamnestic) response
immune response when re-exposed to the same antigen
during an anamnestic response, how quickly do memory B cells become plasma cells?
within hours of re-exposure
describe the IgG titer during a secondary response
rises sharply and peaks in a few days
during an anamnestic response, low levels of Ig__ are also secreted and then quickly decline
M
after a secondary response, IgG levels remain elevated for…?
weeks to years; conferring long lasting protection
memory does not last as long in ____ immunity as in _____ immunity
humoral, cellular
autoimmune diseases
failures of self-tolerance; immune system does not correctly distinguish self-antigens from foreign ones and produces auto- antibodies that attack body’s own tissue
auto-antibodies
attack one’s own body tissues
three reasons for failure of self-tolerance
- cross-reactivity
- abnormal exposure of self-antigens in the blood
- changes in structure of self-antigens
failures of self-tolerance: cross-reactivity
some antibodies against foreign antigens react to similar self-antigens
example of cross-reactivity
Rheumatic fever - streptococcus antibodies also attack heart valves
failures of self-tolerance: abnormal exposure of self-antigens to the blood
some of our native antigens are not normally exposed to blood
failures of self-tolerance: changes in structure of self-antigens
viruses and drugs may change the structure of self-antigens or cause the immune system to perceive them as foreign
severe combined immunodeficiency disease (SCID)
hereditary lack of T and B cells; vulnerability to opportunistic infection and must live in protective enclosures
acquired immunodeficiency syndrome (AIDS)
non-hereditary diseases contracted after birth
AIDS is caused by
human immunodeficiency virus (HIV)
HIV invades…(3)
helper T cells, macrophages, and dendritic cells
how does HIV invade cells?
‘tricking’ them to internalize viruses by receptor-mediated endocytosis
HIV is a retrovirus, meaning…
it sues the viral enzyme reverse transcriptase to convert its viral RNA genome into DNA which can be inserted into the host genome
how does HIV cripple the entire immune response? (2)
by (1) taking out helper T cells and (2) causing them to be vulnerable to opportunistic infections
early signs of AIDS
flu-like symptoms of chills and fever
progressive symptoms of AIDS (4)
night sweats, fatigue, headache, extreme weight loss, lymphadenitis
AIDS helper T cell count
200 cells/uL compared to 600-1200 cells/uL
opportunistic infections include (5)
- toxoplasma
- pneumocystis
- herpes simplex virus
- cytomegalovirus
- tuberculosis
how is HIV transmitted? (5)
- blood
- semen
- vaginal secretions
- breast milk
- across the placenta
therapy for aids
antiretroviral therapy (ART) maintains near-normal life expectancy
COVID-19 (coronavirus disease of 2019)
global pandemic of 2020-2021
COVID-19 is caused by…
SARS-CoV-2
viral structure of SARS-CoV-2 (4)
(1) single strand RNA stabilized by (2) RNA-binding nucleocapsid (N) protein and surrounded by (3) outer lipid envelope studded with (4) projecting spike proteins
SARS-CoV-2 infection cycle (2)
- virus in inhaled and invades great (type II) alveolar cells by binding to ACE2 receptors
- virus replicated in host cells, and new ones are releases to infect new cells
mechanisms of disease - SARS-CoV-2 (3)
- body cells with ACE2 receptors are infected (heart, kidneys, digestive tract, blood vessels, brain)
- cytokines released by immune cells activate inflammation
- potential cytokine storm produces hyperinflammatory response
COVID-19 symptoms (4)
- flu-like symptoms
- loss of taste and smell
- possible breathing difficulty
- low blood oxygen
what is the most effective way to prevent critical illness and halt the spread of COVID-19?
VACCINATION
