Transcript Immune System: Autoimmune Diseases

Immune System:
Autoimmune Diseases
Review Question
What is the function of
T-cells?
Review Question
What is the function of
B-cells?
Review Question
What is the difference
between natural and
artificial immunity?
Review Question
What is the difference
between active and passive
immunity?
Vaccination
A preparation containing antigenic material:
 Dead microorganism
 Weakened microorganism- virus can only reproduce a
few times in body- can’t cause disease
 Part of virus or bacteria that contains antigen
 Toxoid (harmless form of toxin of bacteria)
Vaccination
Why aren’t they always effective?
 Natural infections persist within the body for a long time
so the immune system has time to develop an effective
response, vaccinations from dead m-os do not do this.
 Less effective vaccines need booster injections to
stimulate secondary responses
Vaccination
Why aren’t they always effective?
 Some people don’t respond well/at all to vaccinations
1. Defective immune systems
2. Malnutrition, particularly protein
Vaccination
Why aren’t they always effective?
 Antigenic variation caused by mutation
 Antigenic drift – mutations arise in genes for antibodies,
new strains of virus created over time (Influenza)
 Antigenic shift – large changes- two or more strains
combine, new virus has combo of antigens and is
unrecognizable by host
Vaccination
Why aren’t they always effective?
 No vaccines against protists (a protist causes malaria)
 Many stages to Plasmodium life cycle with many
antigens so vaccinations would have to be effective
against all stages
Vaccination
Why aren’t they always effective?
 Antigenic concealment parasites live inside body cells
 Plasmodium – liver and blood cells
 Parasitic worms – cover themselves in host proteins
 HIV – live inside T-helper cells, highly complex and
changeable
Smallpox
Symptoms
 Red spots containing transparent fluid all over body.
 Spots fill with pus
 Eyelids swell and become glued together
Smallpox
Mortality
 12-30% died
 Survivors often
left blind and
disfigured with
scabs.
Smallpox
Eradication program
 Started by WHO in 1956
 Aimed to rid world of smallpox by 1977
 Involved vaccination and surveillance
 Over 80% of populations at risk of the disease were
vaccinated
Smallpox
Eradication program
 After any reported case everyone in the household and
30 surrounding households vaccinated – RING
VACCINATION
 Last case of smallpox reported in Somalia in 1977
 World declared free of smallpox in 1980
Smallpox
Eradication program – why was it successful?
 Variola virus stable  cheap as everyone used same vaccine
 Vaccine made from harmless strain of similar virus (vaccinia)
 Easy to identify infected people
 Smallpox doesn’t lie dormant in body
Smallpox
Why wouldn’t an eradication program always work?
Smallpox
Why wouldn’t an eradication program always work?
 Political instability
 Poor infrastructure
 Cost
 Difficult to diagnose before disease spreads
 Rapid mutation of disease
 What happens when the body’s
lymphocytes fail to recognize its own
cells and tissues, and begin attacking
them?
 AUTOIMMUNE DISEASES
Autoimmune Diseases
 Failure of antibodies and T cells to
recognize own cells
 Antibodies and T cells launch attack
against own cells
 Defenses either overreact to
antigens or fail to react to an antigen
Hypersensitivity
 Hypersensitivity is an excessive
response or overreaction of the
immune system
 Types= allergy, autoimmunity, and
isoimmunity
Allergy
 Hypersensitivity of immune system to
harmless environmental antigens
(allergens)
 Many are genetically predispositioned
 Susceptible person must be exposed
multiple times to allergen- triggering
production of antibodies
Allergy
 Exposure to allergen causes antigen-antibody
reactions that trigger release of histamine and other
inflammatory chemicals in body
 Histamine causes blood vessels to widen and become
leaky.
Allergy
 Fluid and white blood cells leave capillaries.
 The area of leakage becomes hot, red and inflamed
 Antihistamines can be used to relieve symptoms
Allergy
 Are allergies all bad?
 Could there be benefits?
Allergy
 Allergies are not “bad”; but body’s way of protecting
itself from potential harmful invaders
 Allergic reactions expel allergen from body
 Allergic reaction is like alarm system for body
 How would allergies have been helpful to our
ancestors?
Allergy
 Many allergens can destroy cells (toxins, venom, etc)
 Body starts producing IgE (antibody) after first
exposure of allergen starts harming your cells
 After you produce specific antibodies to the allergen,
your body is oversensitive to it, prepared to
immediately react and rid itself of the allergen if
exposed again
Autoimmunity
 Incorrect and excessive immune response to “selfantigens”
 Body attacks itself
 Examples of diseases:
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
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Diabetes type 1
Hypothyroidism
MS
Rheumatoid arthritis
Lupus
Isoimmunity
 Undesirable reaction of the immune system to antigens
from different individual of the same species
 Can happen during:
 Pregnancy
 Organ or tissue transplant
Isoimmunity during pregnancy
 When antigens from fetus enter
mother, sensitizing mother’s immune
system
 Antibodies then form in the mother
 If they enter the fetus’ blood supply
they can cause inappropriate
immune reaction
Isoimmunity during pregnancy
-
 Erythroblastosis fetalis: Rh mother
and Rh+ fetus
Immune Deficiency
 Immunodeficiency= failure of immune
system to defend against pathogens
 Normally disrupts function of B and T
cells
 Allows more infections and cancer to
form, that ultimately kill the patient
 Two types: Congenital and Acquired
Congenital Immune deficiency
 Rare; results from improper development of
lymphocytes from birth
 Can cause insufficiency or absence of antibodies in
blood
 Can be treated with antibody injections and bone
marrow transplants
Acquired Immune Deficiency
 Develops after birth
 Best example: AIDS, caused by the virus HIV
 Human Immunodeficiency virus
Human Immunodeficiency virus
 HIV thought to have entered humans between 1914
and 1940
 In 1983, the retrovirus was identified as the cause of
AIDS
 HIV infects Helper T cells (most important WBC in
identifying infections)
HIV
 Retrovirus containing RNA, high rate of mutation
 Tricks host cells into letting it into the Helper T cell
 Reverse transcription codes RNA into DNA
 New viral DNA gets spliced into cell’s DNA, taking over
machinery of cell
 New HIV virions are synthesized and released from the
cell
HIV
 Helper T cells die as HIV takes over the cell
 More lymphocytes are lost as disease progresses
 Some drug therapy exists to repress the spread of the
virus by blocking its entrance into healthy cells or
slowing its reproduction in the cell
What does HIV look like?
 Initial infection- flue like symptoms a few
weeks after infection
 Stage 1-HIV positive with no symptomscan stay at this stage for up to 10 years,
but can still pass on virus (virus replicates
slowly with drug therapy)
What does HIV look like?
 Stage 2-HIV positive with symptoms- T
cell count= less than 200 per microliter of
blood person is diagnosed with AIDS
 Symptoms= swollen glands, diarrhea, loss of
weight and appetite, fever, fatigue, skin
rashes, night sweats, oral thrush
 Life expectancy= 2 to 5 years
What does HIV look like?
 Stage 3- Full blown AIDS
 Patient dies of infections that take advantage
of weakened immune system
 Patient dies in a matter of months
 AIDS related illnesses include cancers and
pneumonia