Immune System (Ch 23) Flashcards
Function of the immune system
- Kills infectious organisms
- Recognizes and tolerates self cells and non harmful foreign molecules
- immunological memory to prevent re-infection from same organisms
Parts of the immune system
lymphatic system, thymus, spleen, tonsils, peyers patch, and bone marroe
Function of the lymphatic system
Drains excess interstitial fluid to lymphatic vessels, returns to bloods
When pressure increases in the lymphatic vessels…
spaces between lymph endothelial cells close to prevent fluid coming out
function of the lymph nodes
recognize pathogens and some bacterial toxins that get into the lymph
Edema
from fluid accumulating in the interstitial space
Hypertension (causes of edema)
increased capillary hydrostatic pressure pushes more fluid out of capillaries
Kidney Disease (causes of edema)
kidneys don’t properly excrete salts and water; so build-up occurs
Heart Disease (causes of edema)
Valve failure, obstruction and heart failure causes high venous pressure, lack of venous return
Skeletal Pump (causes of edema)
long periods of standing, immobility/paralysis causes more fluid retention in veins and lymphatic system
Medications (causes of edema)
affect blood pressure, vascular resistance, autonomic nervous system, kidney function and osmotic balance
plasma proteins (causes of edema)
Low albumin can be caused by wounds, burns, liver diseases or malnutrition
Blocked lymph vessels (causes of edema)
due to cancer, infection, inflammation or surgical removal
Red bone marrow
located in central flat bones and ends of long bones
contains hematopoietic stem cells (Pluripotent) that produce red and white blood cells and platelets (Thrombocytes)
Myeloid Lineage (white blood cell)
innate immune system cells, RBCs and megakaryocytes (for platelets)
Lymphoid Lineage (white blood cell)
adaptive (aquired) immune system cells, NKs
B cells (lymphocytes)
Mature in bone marrow then migrates to spleen or lymph nodes\
- responsible for “humoral response”
- phagocytic snd antigen presenting
T cells (lymphocytes)
originates in bone marrow then migrate to the thymus to mature then migrates to spleen or lymph nodes
- responsible for “cell-mediated response”
- recognize microorganisms and viruses by specific antigens on their surfaces
Antigens
part of molecules that cause an immune reaction or immune cells raise antibodies against
Function of B and T cells
recognize self-antigens, our bodies remove the ones that recognize self antigens or harmless substances or our microflora
they react only to specific molecules that match their specific receptors
Negative selection
Thymocytes (immature T cells) that bind the self-proteins are destroyed
Thymus epithelial cells
express self-proteins found in other body regions
Immune cells
B and T cells, macrophages, and dendritic cells
recognize pathogens, some toxins, and dead cells carried in the lymph
Reticular fibres
slow and filter lymph and trap particles that may be recognized by immune cells
Spleen function
filters blood, not lymph, but contains lymphocytes
red pulp (in spleen)
contains macrophages, red blood cells, and platelets. breaks down old red blood cells
white pulp (in spleen)
contains B and T cells, macrophages and dendritic. also contains reticular fibres
Lymphatic nodules
- similar to nodes but not surrounded by capsule
- higher in number where pathogens may enter
- Ex. tonsils, andenoids, Peyer’s patches (gut-assosiated lymphoid tissue (GALT))
Microflora (microbiome)
- microorganisms that normally live on us and in us (don’t cause disease)
- works with our immune system
- helps your immune system to tolerate non-pathogenic microorganisms
- helps fight pathogens by establishing themselves first, limiting available binding sites and resources for pathogens
- also alters the environment to make your body less hospitable
innate immune response
- defense which responds in a non specific way to infection
- doesn’t provide long term protection, but triggers cells involved in the adaptive immune response to provide long term protection
First line of defense is preventing infection
skin and mucus are a physical barrier. and covered with the microflora
Skin
had specialized immune cells throughout its layers to detect invasion or destroy invaders
Musus
found in digestive and respiratory systems (nose hairs also filter particles and induce sneezing)
Skins chemical and physical defenses
- oil glands (sebaceous) make the skin surface acidic
- saliva, sweat, snd tears contains lysozyme that attacks and digests the cell walls of many bacteria
- skin produces RNAase which degrades RNA from microorganisms especially RNA viruses
Digestive/Respiratory systems mechanisms to prevent infection
- saliva contains lysozyme
- Hydrochloric acid and digestive enzymes protect the digestive tract.
- Mucus traps most microorganisms in the respiratory tract, and cilia
continually move mucus up toward the throat (swallowed or coughed
out). - Resident bacteria, normal microflora in the digestive tract, help prevent infections.
Second line of defense
When a foreign pathogen enters the
body, the immune system detects antigens on the surface of the pathogen
cellular and chemical defenses
- Cells that kill invading microbes
- Proteins that alert other cells to the invasion
- Proteins that kill invading microbes
- The inflammatory response
- The temperature response
Cytokines
secreted by Infected cells or those that detect the infection
- signals proteins
that alert neighbours and nearby immune cells to the infection
- positive feedback loop
Autocrine
act on the releasing cell
paracrine
act on nearby cells
Chemotaxis
Innate immune cells move toward the infection following the increasing concentration of
cytokines
Cytokines can cause immune cells to…
proliferate, differentiate, or trigger other functions.
Neutrophils
- Usually the first cells to arrive at an infection. Migrate from the bloodstream through capillaries.
*The most numerous type of white blood cell.
*Secrete cytokines to attract other immune cells and increase vascular permeability.
*Engulf bacteria (phagocytosis) and attack them with enzymes and chemicals in specialized compartments.
Monocytes
are attracted to the infection (chemotaxis)
1. Macrophages
2. Dendritic cells
- both do clean up and antigen presenting.
Macrophages
specialized to engulf and remove microbes and debris from cells or dead bacteria. Clean-up crew. Help dampen the immune response once the infection is over.
Dendritic cells
specialized to display foreign invader’s antigens on their surface to B and T cells
Natural Killer Cells
- kill cancerous and virus-
infected cells by creating holes in
their plasma membranes with
perforin. - The holes allow cell-killing proteins
from the NK cell and interstitial fluid
to enter the cell. - This kills the cell directly or induces
apoptosis. - Macrophages and dendritic cells
then phagocytize the cell debris to
remove it
interferons
- secreted by cells infected by
viruses or bacterial toxins - activate NKs in infected areas
- can activate p53 in infected cells to cause apoptosis
neighbouring uninfected cells respond by
- producing proteins that inhibit viral replication
(true or false) some viruses prevent our cells from making interferons
true
What are parly responsible for making you feel unwell when you are sick?
interferons
plasma proteins made in liver
Inactive state until they encounter a fungi, bacteria or any antibody-covered microbe
Activated complement proteins
- bind microbes and increase phagocytosis
- stimulates mast cells to release histamine which increases vasodilation, vascular permeability, attracts phagocytes
complement proteins
form a membrane attack complex (MAC); makes a pore in the foreign cell’s membrane, fluid rushes in and kills the cell
membrane attack complex (MAC)
similar function to perforin, but it uses different proteins and acts
only on foreign cells, so it’s not the same
Inflammation
triggered by physical damage, toxins, and/or infection
- often recognize tissue-specific inflammation
Classical Signs
- redness, swelling, pain, heat and reduced function.
- Caused by vasodilation, vascular permeability and signals released by
damaged cells and immune cells
Acute Inflamation
- short lived, localized, adaptive response
- esolves once repair is complete or infection is cleared and can promote tissue regeneration
Chronic Inflammation
- Immune system continually attacks tissues and produces cytokines
- collateral damage caused by immune cells damages the tissue and doesn’t resolve properly
Mast cells and basophils release
histamine and prostaglandin in damaged tissue
- cause vasodilation and
increase capillary permeability
Prostaglandins
activate pain sensors
Aspirin and ibprophen
inhibit prostaglandin production, used to limit pain and swelling
if blood vessels are damaged…
platelets convert fibrinogen in plasma into fibrin that makes blood clots. This also helps to trap pathogens and limit their spread.
Neutrophils and macrophages
easily migrate from the dilated blood
vessels and kill microbes and engulf
dead cells, as well release more
chemokines and cytokines
Pus is a mixture of…
bacterial, dead cells, and white blood cells
Phagoctyes
clean up dead cells and microbes/debris and the tissue heals as new cells are made
Classic/cardinal signs of inflammation
- Redness (increased blood flow)
- Swelling (increased vascular permeability causing edema)
- Pain (edema due to prostaglandins presses on pain sensors or neurons
are injured) - Heat (increased blood flow, and increased metabolism of nearby cells
and immune cells)
Your body temp set point is determined by the…
hypothalamus
Pryogens
substances that trigger a fever. May be cytokines, prostaglandins or toxins made by the invading organism.
what signals the hypothalamus to raise body temp? (fever)
activated immune cells releasing cytokines
what are the fever thresholds
fever ≤ 39.4ºC - normal
fever > 39.5ºC - can be treated
fever > 42ºC - fatal
Why can fevers be dangerous?
if temp is too high, it begins to inactivate the body’s cellular enzymes
cells in the adaptive immune response
B cells, plasma cells, helper T cells, cytotoxic T cells, regulatory T cells
antigen-presenting cells
monocytes differentiate into macrophages or dendritic cells (DCs), which along with B cells (before differentiation)
Macrophages or DCs recognize pathogens by…
pathogen-associated molecular patterns (PAMPs), which are not found on human cells
what have both MHC I and MCH II surface proteins?
antigen-presenting immune cells
- use both to present antigens to lymphocytes and activate them
nucleated cells have what are on their surface?
major histocompatibility complex I (MHC I) proteins on their surface that the immune system recognizes as “self”
- everyone’s MHC signature is unique
Activated macrophages/DCs alert other immune cells by…
the digested microbe fragments that are displayed on their MHC proteins
infected cells display…
microbe parts on their MHC I proteins to cytotoxic T cells that will kill them.
- Normal cells display self-proteins that are ignored.
CD4+ helper T cells
- Only activated by antigens presented on MHCII by APCs
- Do not kill pathogens or infected cells.
- Secrete cytokines to activate B cells, cytotoxic T cells, NK cells, and macrophages.
- Some types dampen immune response or help produce tolerance
- CD4+ cells are targeted by HIV (other immune cells also make CD4).
CD8+ Cytotoxic T cells
- Activated by antigens presented on MHCI molecules.
- Kill virus-infected cells, cancer cells, or transplanted cells with perforin (same as NKs)
or by inducing apoptosis. - Cytotoxic T cells generally fight intracellular infections by killing the infected cells.
- Migrate between lymph and tissues.
what does an APC with a foreign antigen displayed do?
eaves the site of infection and travels the lymphatic system until it encounters a helper T cell whose receptor matches the antigen.
APC secretes
nterleukin-1 (IL-1), which activates the helper T cell.
Helper T cell secretes
IL-2, which acts on itself stimulating proliferation and differentiation
4 helper T cell subtypes
1)TH1 cells
2)TH2 cells
3)Regulatory T cells (Tregs), also called TH17
4)Tolerant T cells (TH3) help create tolerance and do not react to antigens. High
exposure to an antigen, such as food, normal flora bacteria, and harmless
environmental molecules helps produce TH3s, especially oral exposure.
TH1 cells
increase cytotoxic T cell activation for virus-infected cells.
TH2 cells
increase B cell activation (antibodies) for a bacterial infection.
Regulatory T cells (Tregs) (TH17)
slow down the immune response at
the end of infection or prevent reactions against self-antigens.
Tolerant T cells (TH3)
help create tolerance and do not react to antigens. High exposure to an antigen, such as food, normal flora bacteria, and harmless
environmental molecules helps produce TH3s, especially oral exposure.
Memory Cells
fight the same infection in the future
antibodies have how many binding sites
2
functions of antibodies
- Cause agglutination (clumping) - microbes can’t function properly in clumps.
- Opsonized pathogens are more easily phagocytized by macs, DCs, and neutrophils.
- antibody binding a virus-infected cell targets them for killing by NKs
- Antibody-bound pathogens activate complement and can be killed by the membrane attack complex
secondary immune response
adaptive immune response to a previously encountered
antigen
Naturally acquired active immunity
Contracting an active infection that produces memory cells
Naturally acquired passive immunity
A mother transfers antibodies to the baby through breast feeding.
Antibodies are against an infection the mother had previously
encountered
Artificially acquired active immunity
Vaccination producing memory cells without causing disease
Artificially acquired passive immunity
Transferring antibodies to a person by injection. Temporary immunity to
the specific antigen.
Vaccination
introducing a dead or inactivated pathogen, or protein fragments into the body, that stimulates the adaptive immune response
Live Attenuated Vaccines
Prepared from attenuated (weakened) strains that are almost or completely devoid of pathogenicity, or a closely related virus, but still induce a protective immune response.
Killed Vaccines
- The most common type of traditional vaccine.
- Virus grown in a lab on cultured cells and harvested
Toxoid Vaccines
- Toxin-producing microbes grown in a lab and the toxin harvested and
purified. - Chemically-inactivated toxic compound is used as vaccine.
- Vaccine targets the toxin rather than the microorganism
Subunit Vaccines
Recombinant DNA technology can express immunogenic pathogen proteins in other organisms
- These proteins can then be used to make the vaccine with no worry of infection from the whole pathogen
Adenovirus Vaccines
- An immunogenic protein gene from a different virus is inserted into replication-deficient adenovirus
genome. - Modified adenovirus is grown in the lab using special cells to make it replicate.
mRNA Vaccines
- use mRNA coding for the COVID-19 spike protein.
- mRNA is engulfed in lipid nanoparticles. After injection, our
cells take up the mRNA-nanoparticles by phagocytosis
Autoimmune disease
the immune system attacks its own body’s cells as if they were foreign. May attack a specific cell type or a tissue.
what happens to B and T cells for those who have autoimmune disease?
the cell receptors bind to self-
proteins as though it were a foreign antigen.
when gender is affected by autoimmune disease more?
Female (two-thirds of cases).
Hygiene hypothesis
lack of infections and/or lack of exposure to commensal microbes contributes to an increase in autoimmune and allergic diseases.
what population has an increased risk of asthma and allergies?
Children who require antibiotics early in life
Molecular mimicry (Autoimmune disease)
The immune system will sometimes cross-react with very similar antigens. It’s possible that the immune system
will cross-react with a self-tissue after fighting some infections
Improper lymphocyte negative selection (Autoimmune disease)
If negative selection for self-tolerance fails, some self-reactive cells will move to the secondary lymphatic tissues and can react with self-proteins
Genetic factors (Autoimmune disease)
ome variations of certain MHC genes affect antigen presentation. Other genes involved in immunity could also play a role,
Gender (Autoimmune disease)
More females tend to have autoimmune diseases. May be due to hormonal differences or differences in how the immune system works in males vs females. No one single factor has been identified
Latitude/ Vit D (Autoimmune disease)
- Regions with more UV light
exposure have lower incidence of
some autoimmune diseases
compared to northern or southern
regions. - Vitamin D is a possible factor. It
plays an important role in immune
regulation, but supplementation
does not treat autoimmune
disease
What are allergies?
immune system reacting to harmless foreign antigens as though
they were pathogens
Allergies are what kind of reaction?
hypersensitive
Allergies cause
causes vasodilation,
bronchoconstriction, mucus
production, itching, sneezing, and
watery eyes
Anaphylaxis
severe allergic reaction
what is needed for someone thats having anaphylactic shock?
require injection of epinephrine (e.g. EpiPen) to dilate bronchioles, reduce swelling and increase blood pressure
An injection of epinephrine only lasts
20 mins
- gives you time to get help/ambulance.
Allergy treatment involves
antihistamines and/or corticosteroids
severity of an allergic reaction depends on…
how the immune system was sensitized, the type of allergen,
and its mode of entry into the body.
multiple sclerosis affects…
myelin on axons in CNS
Type 1 diabetes affects…
beta islets cells on pancreas
celiac disease affects…
small intestine microvilli in cross-reaction with gluten
Addison’s disease affects…
adrenal cortex
aplastic anemia affects…
bone marrow
crohns disease affects…
GI tract
Ulcerative Colitis affects…
Large intestine
Graves disease affects…
thyroid gland (hyperthyroidism)
Hashimotos disease affects…
Thyroid gland (hypothyroidism)
Lupus affects…
many tissues
myasthenia gravis affects…
skeletal muscle
rheumatoid arthritis affects…
joints
Psoriasis affects…
Skin
