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Immunity
What is it? - The body’s ability to fight pathogens.
Types of immunity:
1. Innate immunity – genetically determined
2. Acquired immunity – not present at birth but instead arises by active or passive means
3. Active immunity – a consequence of the immune response; exposure to an antigen (natural
exposure or induced exposure)
a. Naturally acquired active immunity – begins to develop after birth and inhanced as new
pathogens are encountered
b. Induced active immunity – antibody production is stimulated under controlled conditions;
hence immunizations with vaccines
4. Passive immunity – produced by the transfer of antibodies to an individual from another source
a. Naturally acquired passive immunity – antibodies produced by a mother during
gestation (placenta) or in early infancy through breastmilk.
b. Induced passive immunity – antibodies are administered to fight infections after
exposure (rabies, chicken pox of your parents, small pox/cow pox, etc.)
Properties of immunity:
1. Specificity – specific defense mechanism is activated by a specific antigen (T cells and B cells
have receptors for specific antigen)
2. Versatility – your immune system produces millions of different lymphocytes to be ready for
anything
3. Memory – your immune system remembers the antigens it encounters; creates “memory cells”
4. Tolerance – when the immune system does not respond to some antigens because they are
the “normal” ones in the body
Hormones of the Immune System:
1. Interleukins (IL) – widespread effects; increase T cell sensitivity to antigens, stimulate B cell
activity and antibody production, enhance nonspecific defenses (inflammation or fever), some
suppress immune function
2. Interferon – make the cell synthesizing them and its neighbors resistant to viral infection, slow
the spread of the virus, used to treat some cancers and MS
3. Tumor necrosis factors (TNFs) – slow tumor growth and kill sensitive tumor cells
4. Phagocytic regulators – coordinate the specific and nonspecific defenses by adjusting the
activities of Phagocytic cells
5. Colony-stimulating factors (CSFs) – stimulate the production of blood cells in the bone marrow
and of lymphocytes in lymphoid tissues and organs
Autoimmune Disorders: develop when the immune response mistakenly targets normal body cells
and tissues; “autoantibodies”; (rheumatoid arthritis, insulin-dependent diabetes mellitus, multiple
sclerosis, etc.)
Immunodeficiency diseases: the immune system fails to develop normally or the immune response
is blocked; some are born with it (severe combined immunodeficiency disease) and some get it from
a viral infection (AIDS)
Allergies: inappropriate or excessive immune responses to antigens
Types of pathogens:
1. Fungus – Fungi – heterotrophic eukaryotes that acquire their nutrients by absorption (yeast,
molds, mushrooms, etc.)
a. 30,000 species are parasitic; Animals usually less susceptible to parasitic fungi than
plants; fungal infection is called mycosis
b. They can cause serious problems as agricultural pests; Consumption of ergot-infested
flour can cause gangrene, nervous spasms, burning sensations, hallucinations, temporary
insanity, and death.
c. Cause infections :athlete’s foot, ringworm (treated with fungicidal lotions and powders),
and vaginal yeast infections (an opportunistic pathogen – a normal inhabitant of the body
causes problems when some change in the body’s’ microbiology, chemistry, or
immunology allows the yeast to grow unchecked)
2. Bacteria – pathogenic bacteria cause about ½ of all human diseases
a. Most cause poisons (endotoxins and exotoxins)
b. Exotoxins: Staphylococcus aureus (staph) causes a skin surface infection; It is usually a
harmless resident of our skin surface, but entering the body can cause illness; E. coli can
cause illness and death
c. Endotoxins: not cell secretions, but components of the cells walls of bacteria; same
general symptoms including fever, aches, blood pressure drop; Salmonella
d. Can be used as biological weapons; anthrax (bioterrorism); many nurses and doctors are
trained to deal with this issue no; soldiers are treated for it
3. Parasites - disease-causing organism that lives on or in a human or another animal and
derives its nourishment from its host
a. Helminths – in the body - Flukes, flatworms, tapeworm, roundworm
b. On the body - Lice
4. Protozoa – one celled organisms;
a. many live in the GI tract and cause disease (from contaminate water, food, etc.); can
cause diarrhea that can be mild or harmful; one can cause an STD - Trichomonas
vaginalis
5. Prions - an abnormal, transmissible agent that is able to induce abnormal folding of normal
cellular prion proteins in the brain; leads to brain damage. Usually rapidly progressive and always
fatal.
b. Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of
rare progressive neurodegenerative disorders that affect both humans and animals.
Long incubation periods, characteristic spongiform changes associated with neuronal
loss, and a failure to induce inflammatory response. (Mad Cow Disease)
6. Viruses – genes packaged in proteins.
a. New viral DNA and protein molecules then assemble into new phages that burst from
the host cell; Emerging viral diseases pose a threat to human health (HIV, AIDS, etc)
b. Many cause disease when they invade animal or plant cells; Some can remain latent in
the host’s body for long periods
c. Virus studies helped establish molecular genetics; now molecular genetics helps us
understand viruses.