Chapter 17 The Immune SystemAnd Diseases

Anatomy and Physiology

Lymphatic System• Drain excess fluid.• Transport dietary lipids.• Carry out immune response.• Consist of veins and capillaries similiar to

blood vessels.• Contain lymph nodes to filter interstitial

fluid.

Lymphatic organs and tissues• Thymus- two-lobed organ, located medial

to the lungs and superior to the heart, contains T cells and macrophages, clear dead and dying cells

• Lymph nodes- 600 bean shaped nodes, B cells, T cells, macrophages, filter lymph and circulate lymph through valves and vessels

Lymphatic Organs and Tissues

• Spleen- between stomach and diaphragm, lymphocytes and macrophages, macrophages destroy pathogens, storage of platelets, production of fetal blood cells, B and T cells carry out immune responses

Lymphatic Organs and Tissues

• Lymphatic nodules are egg shaped, tonsils• 5 tonsils• Pharyngeal, adenoid, two palatine tonsils

(obvious ones) 2 lingual tonsils at the base of the tongue.

Barrier Defenses-non-specific

• External barriers prevent pathogens from entering the body:

• Skin• Mucous membranes• Saliva• Tears

• Cilia• Hair• Sweat• oil

Internal Defenses

• Interferon- protein that interferes with virus replication

• Complement system- proteins that enhance other immune responses, normally inactive

• Natural killer cells- kills microbes and tumors

• Phagocytes- ingest microbes

• Macrophages- developed from monocytes, eat microbes

Inflammation and Fever Responses• Helps prevent the spread of microbes.• Allows more blood to flow to the injury site.• Helps remove toxins.• Carries immune cells to the site faster• Fever is caused by interleukins.• Elevated body temperature increases the

effects of interferon, and speeds up bodily reactions and repair.

Vocabulary Cards

Inflammation

Interferon

Macrophage

Natural killer cells

Phagocyte

Non-specific immune response

Lymphocytes-Specific response

• B and T cells.• Contain antigen receptors.• Cell-mediated response- directly attack

invaders• Antibody mediated response- release

antibodies against the microbe.

Antigens and Antibodies• An antigen causes the body to produce

antibodies.• Specific T cells will react to certain

proteins and toxins.• MHC molecules (major histocompatibility

complex)-unique proteins that identify you to help T cells recognize foreign invaders.

• Major roadblock to organ transplantation.

Antigens and Antibodies• Antigens induce plasma cells to secrete

proteins called antibodies against them.• The antibody fits against the antigen on

the surface of the microbe.• Antibodies belong to a group of proteins

called immunoglobulins.• Each has a distinct function and chemical

structure.

T Cells• The presence of antigens inform

the T cells to begin attack but it only becomes active once the foreign antigen binds with it.

• APC or antigen presenting cell must ingest a foreign antigen, process it and present it to a T cell for recognition. Dendritic cells, helper T cells and macrophages can do this.

T Cells• T cells also need a second stimulator

to prevent false alarms. Interleukin does this.

• Once activated, the T cell clones itself into an army.

• Causes swollen lymph nodes.

3 types of T Cells

• Helper T cells release interleukins and also offer antigens.

• Cytotoxic T cells kill cells that are infected with precision using enzymes.

• Memory T cells remain in the body to prevent reinfection.

B cells• Usually stay in the lymph nodes.• Secrete antibodies once activated

by T cells and interleukins.• Can receive unprocessed

antigens but respond faster to processed ones

• Can become memory cells to respond to the same antigen in the future

Immunity• Naturally Acquired Active- get sick,

memory cells remember and prevent future attacks

• Naturally Acquired Passive- Antibody transfer from mother to fetus across placenta, or breastfeeding

Immunity• Artificially Acquired Active- vaccinations

cause an immune response without causing sickness, usually involves injecting antigens or weakened viruses

• Artificially Acquired Passive- injection of immunoglobulins (antibodies)

Vocabulary Cards

B cell

T cell

Antigen

Antibody

Memory cell

Vaccine

MHC

APC (antigen processing cell)

40 total cards

B cellT cellAntigenAntibodyMemory cellMHCAPCSpecific immune response

Pathogenic Diseases of the Human Body

Virus structure• The structure of a virus is well suited to its

function; entering a host cell and reproducing.

• A virus is composed of a relatively short piece of nucleic acid DNA or RNA surround by a protein coat.

• Since a virus doesn’t have its own cellular machinery, it must use the host cell’s machinery to make copies of itself.

T-4 bacteriophage

Virus replication• Viruses that infect bacteria called

bacteriophages reproduce in 2 ways. This will be used as our example.

• In the lytic cycle, the phage attaches to the host cell and injects its DNA.

• The host cell’s enzymes and synthesis machinery make copies of the viral DNA and the viral proteins.

• The viral proteins and nucleic acids then assemble themselves inside the host cell making copies of the original infecting virus.

• The host cell then bursts open and these offspring infect new host cells and repeat the cycle.

Virus replication• In the lysogenic cycle, a virus injects it genes into

the host. • The viral DNA then adds itself directly to the host

cell’s DNA. • Each time the host cell reproduces, the viral DNA

is copied along with the host’s DNA.• Occasionally, the viral DNA separates from the

host DNA and starts a lytic cycle.• New phages are made and released.

Lytic and lysogenic cycles

Using Phages to Help• Although bacteriophages are viruses, since

they don’t attack humans they are useful to help humans combat bacterial infections.

• Many antibiotics are no longer useful because bacterial develop resistance to them.

• Developing new antibiotics to deal with these “superbugs” is costly and doesn’t always work.

• Attack good and bad bacteria

• Affect the whole body and “wear off”

• Multiple side effects• Bacteria develop

resistance• Time consuming to

create new antibiotics

Bacteriophages Antibiotics

• Very specific and only attack intended bacteria

• Site specific, where they are needed

• No side effects reported

• Not many resistant bacteria

• Easy to find new phages

Viruses and disease• Some viruses use RNA as their genetic material.• Some viruses that use RNA are flu, the common

cold, measles, mumps, HIV, and polio.• DNA viruses are herpes and hepatitis.• The way viruses cause disease is radically different

from bacterial infections.• A virus uses the equipment of a host cell to

reproduce therefore approaches to control and cure infection are different from bacterial infection controls.

Viral Diseases/illnesses• Common cold (rhinovirus)• AIDS (HIV)• Measles• Mumps• Herpes (Many forms

including chicken pox)• HPV (Human Papilloma

Virus)• Hepatitis (A,B,C)• Mono• Norovirus

• Bird flu• Ebola and Marburg• Smallpox• Dengue Fever• Yellow Fever• Polio• Lassa Fever• Meningitis (some forms)• West Nile• Rotavirus

HIV: A retrovirus• HIV is a virus that causes AIDS.• It is particularly dangerous because it attacks our

own immune system, the very thing meant to protect us.

• HIV is different because it is called a retrovirus.• A retrovirus synthesizes DNA from RNA which is

the opposite of what normally happens.• An HIV virus carries 2 copies of RNA instead of

DNA.• The RNA then uses an enzyme called reverse

transcriptase to form DNA from the RNA.

• The DNA integrates into the host DNA and takes over.

• The viral DNA can be dormant for years but occasionally it is transcribed into RNA again and new viruses are made.

• While the virus is inactive, the disease symptoms are not evidence.

• Only when the virus reproduces and destroys host cells does an individual get AIDS.

HIV Life cycle

HIV

Where in the world?

History of HIV• The first known case of HIV was from a blood

sample taken from a man in 1959 from the Democratic Republic of the Congo.

• The most common form of the virus is called HIV-1. • This variety appears to have originated in late

1940’s and early 1950’s.• We know the virus existed in the United States

from the mid 1970’s based on reports of strange and rare illnesses that normally don’t affect people with healthy immune systems.

History of HIV• Public health officials first used the

term AIDS in 1982 but it wasn’t until a year later in 1983 that it was discovered that HIV caused AIDS.

• It was first noticed in groups of homosexual men which led to the myth that it was a “gay man’s disease.”

Where did HIV come from?• In 1999, a team of researchers discovered the

original strain of HIV-1, the most common type affecting the developed world.

• It was found in a subspecies of chimpanzee native to west equatorial Africa.

• It was common practice for people the hunt these animals for food and contamination of the people with chimpanzee blood is the mostly likely transmission.

Where did HIV come from?• HIV-2 is a less prevalent strain of the virus more

common in west Africa.• This strain originates from a population of primates

called sooty mangabeys.• These primates are found only in west Africa.• The two strains HIV-1 and HIV-2 have multiple

types of each kind that have mutated over the years.

• All types and strains of HIV descended from SIV which is a similar virus found in several primate species.

Defense against viral diseases

• The immune system is critical to fighting infections and provides the basis for a major medical weapon for preventing certain viral and bacterial infections from occurring.

• This weapon is called the vaccine.• Vaccines are deactivated varieties or small pieces

of pathogens that stimulate the immune system to defend against the actual pathogen.

The first vaccine• The first vaccine was made against the virus that causes

smallpox, an often fatal disease.• Edward Jenner, a physician, discovered that milk maids who

had been exposed to cowpox, a mild disease, were resistant to smallpox.

• The two diseases were so similar that the immune system couldn’t tell them apart.

• Jenner injected people with cowpox which then causes resistance to smallpox.

• Currently, smallpox has been eradicated.• NOTE: Smallpox the disease is gone but not the virus. It’s

“on ice” in a lab somewhere.

Vocabulary CardsLytic cycle

Lysogenic cycle

Retrovirusvaccine

Bacteria have three shapes.• Cocci- spherical shapes that are sometimes

formed in chains, clumps or clusters, Strep throat and pneumonia are this type

• Bacilli- rod shaped such as E. coli that live in your intestines.

• Spirochete- curved or spiral shape, this type causes Lyme disease

Purple or pink?

• Bacteria are stained with two dyes, purple and pink to determine which antibiotics will work for each kind.

• Gram positive retain the purple dye in their cell walls.

• Gram negative do not retain the purple dye but retain the pink dye instead.

• Some antibiotics will only work for one kind.

Gram positive

Gram negative

Bacterial Motility• Flagella- a long thin filament anchored to

the plasma membrane , may be one or many anchored all over the bacteria

• Pili- shorter and thinner filaments that help bacteria stick together in clumps

• NOTE: The flagella and pili are different than the kinds you will observe in eukaryotes.

Most bacteria can copy themselves every 20 minutes!

• Binary fission-DNA duplicates and moves to opposite ends of the cell, then the cell divides

• This method allows quick reproduction and is much simple than mitosis.

• Allows for quick passing of mutant genes. (More on this later!)

Genetic Variation• Since bacteria do not undergo meiosis, they do not

exchange genetic information, however, they can do other things.

• Transformation occurs when some bacteria take up pieces of DNA from the environment and incorporate it into its genetic material.

• In conjugation, two bacterial cells temporarily join and directly transfer genetic material between them.

• Plasmids are separate rings of DNA apart from the cell’s main chromosomes.

• Transduction is when viruses that infect bacteria carry their genes to another.

• They are called bacteriophages. • Some bacteria can survive extended periods of

very hostile conditions by forming specialized resting cells called endospores.

Bacterial Reproduction

How Bacteria Cause Illness• Bacteria and other microorganisms that cause disease

are called pathogens.• Most pathogenic bacteria cause disease by producing

poisons.• Some bacteria produce proteins that cause illness while

others produce cell wall secretion that lead to fever, aches and shock.

Defense Against Bacterial Diseases

• Since the discovery of bacteria, many diseases have declined.

• This is due to better health and sanitation procedures.

• Much of the decline is due to antibiotics.

The first Antibiotic• In 1928, professor Alexander Fleming was

returning from a holiday vacation and noticed he forgot to clean some of his petri dishes in the sink.

• He noticed all the dishes were growing bacteria except one dish that had mold on it was clear.

• The mold inhibited the bacterial growth.• It took many years and other scientists before the

mold Penicillin was purified and available for use.• It became widely used in the 1940’s just in time for

war.

Antibiotic Resistance• Antibiotics have been widely used for 70 years.• Since their introduction, antibiotics are being used

everywhere including our food.• Antibiotics are also overprescribed even when they cannot

help.• Because of this overuse, bacteria are becoming increasingly

resistant to some antibiotics.• These “superbugs” are extremely dangerous because they

can kill the patient but also because they can pass on their resistance to other types of bacteria.

Diseases/Illnesses Caused By Bacteria

• MRSA• TSS (Toxic Shock

Syndrome)• Pneumonia• Gonorrhea• Meningitis• Salmonella• E. Coli• Cholera• Bubonic plague• Botulism• Peptic ulcer• Anthrax

• Typhoid• Staph• Strep throat• Sepsis• Chlamyadia• Tuberculosis• Syphilis• Leprosy• Diphtheria• Tetanus• Rocky mountain spotted

fever• Lyme disease

Vocabulary Cards

CocciBacilli

SpirocheteGram negativeGram positive

FlagellaPili

Binary fissionPlasmid

Antibiotic resistanceconjugation

Diseases caused by Fungi, Prions and protozoans

When it’s not a virus or a bacteria• Prions are proteins that are similar to viruses in

that they aren’t alive and can replicate themselves.• Prions are misfolded proteins that pass on their

mutated folding to other proteins in the body.

Prion Diseases• Human:• Creutzfeldt-Jakob

Disease (CJD)• Variant Creutzfeldt-

Jakob Disease (vCJD)• Gerstmann-Straussler-

Scheinker Syndrome• Fatal Familial Insomnia• Kuru

• Other Animal:• Bovine Spongiform

Encephalopathy (BSE)• Chronic Wasting Disease

(CWD)• Scrapie• Transmissible mink

encephalopathy• Feline spongiform

encephalopathy• Ungulate spongiform

encephalopathy

Fungal Infections• Fungal spores are always present in the air so

fungal infections commonly start on the skin or the lungs.

• Fungus like mushrooms make spores and have roots.

• Many are toxic and release poisons, like toxic black mold.

• Common infections: ringworm, athlete’s foot, and other general skin infections that look like rashes

Parasitic Infections• There are three categories of parasitic infections

that cause disease in humans.• Protozoa, helminthes, and ectoparasites.• Some are unicellular and some are multicellular.• They often have complicated life cycles involving

more than one host.

ProtozoaProtozoa are microscopic, one-celled organisms that can be free-living or parasitic in nature. They are able to multiply in humans, which contributes to their survival and also permits serious infections to develop from just a single organism. Transmission of protozoa that live in a human's intestine to another human typically occurs through a fecal-oral route (for example, contaminated food or water or person-to-person contact). Protozoa that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito or sand fly). The protozoa that are infectious to humans can be classified into four groups based on their mode of movement:•Sarcodina – the amoeba, e.g., Entamoeba•Mastigophora – the flagellates, e.g., Giardia, Leishmania•Ciliophora – the ciliates, e.g., Balantidium•Sporozoa – organisms whose adult stage is not motile e.g., Plasmodium, Cryptosporidium

HelminthesHelminths are large, multicellular organisms that are generally visible to the naked eye in their adult stages. Like protozoa, helminths can be either free-living or parasitic in nature. In their adult form, helminths cannot multiply in humans. There are three main groups of helminths (derived from the Greek word for worms) that are human parasites:

•Flatworms (platyhelminths) – these include the trematodes (flukes) and cestodes (tapeworms).•Thorny-headed worms (acanthocephalins) – the adult forms of these worms reside in the gastrointestinal tract. The acanthocephala are thought to be intermediate between the cestodes and nematodes.•Roundworms (nematodes) – the adult forms of these worms can reside in the gastrointestinal tract, blood, lymphatic system or subcutaneous tissues. Alternatively, the immature (larval) states can cause disease through their infection of various body tissues. Some consider the helminths to also include the segmented worms (annelids)—the only ones important medically are the leeches. Of note, these organisms are not typically considered parasites.

EctoparasitesAlthough the term ectoparasites can broadly include blood-sucking arthropods such as mosquitoes (because they are dependent on a blood meal from a human host for their survival), this term is generally used more narrowly to refer to organisms such as ticks, fleas, lice, and mites that attach or burrow into the skin and remain there for relatively long periods of time (e.g., weeks to months). Arthropods are important in causing diseases in their own right, but are even more important as vectors, or transmitters, of many different pathogens that in turn cause tremendous morbidity and mortality from the diseases they cause.

Malaria• Malaria is a life-threatening disease caused by

parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes.

• In 2015, 95 countries and territories had ongoing malaria transmission,

• About 3.2 billion people – almost half of the world’s population – are at risk of malaria.

• Malaria is preventable and curable, and increased efforts are dramatically reducing the malaria burden in many places.

• Between 2000 and 2015, malaria incidence among populations at risk (the rate of new cases) fell by 37% globally. In that same period, malaria death rates among populations at risk fell by 60% globally among all age groups, and by 65% among children under 5.

• Sub-Saharan Africa carries a disproportionately high share of the global malaria burden. In 2015, the region was home to 88% of malaria cases and 90% of malaria deaths.

• Malaria is caused by Plasmodium parasites. The parasites are spread to people through the bites of infected female Anopheles mosquitoes, called "malaria vectors." There are 5 parasite species that cause malaria in humans, and 2 of these species – P. falciparum and P. vivax – pose the greatest threat.

• P. falciparum is the most prevalent malaria parasite on the African continent. It is responsible for most malaria-related deaths globally.

• P. vivax is the dominant malaria parasite in most countries outside of sub-Saharan Africa.

How would you eliminate Malaria?

Vocabulary Cards• Diseases caused by fungi• Diseases caused by protozoans• Diseases caused by multi-cellular

parasites or carried by them• Diseases caused by prions• Facts on malaria• Cards should have some general

information for test usage. You will be asked about some specifics about well known diseases.