Unit 4 AOS 1 Chapter 8 Immunity

natural immunity

immunity to a disease without any medical intervention.

natural active immunity

• The body’s own immune system encounters a pathogen and responds by producing antibodies and memory cells specific to the pathogen.

• immunological memory is developed: subsequent exposures lead to memory cells proliferating and differentiating so the pathogen is neutralized.

natural passive immunity

• Antibodies are passed on from natural, non-medical intervention, including breastfeeding and via the placenta

• Infant has a weak adaptive immune system; therefore, gains antibodies directly from the mother.

artificial immunity

Immunity to a disease with medical intervention.

artificial active immunity

• Medical intervention required (artificial)

• Introduced pathogen/antigen results in the body producing antibodies (active)

• Vaccines contain weakened/dead microbes/fragments of the pathogen

• Trigger the adaptive immune system

• Immunological memory develops

vaccine

• Vaccines contain components that resemble the pathogens antigens without causing disease.

• Can either be: Attenuated (weakened), Inactivated (dead) pathogens,Toxoids: toxins that have been altered, RNA

• This introduces the individual to the pathogen and allows them to create antibodies and memory cells for a rapid attack.

primary immune response

• Delay in the adaptive immune response after the first vaccination.

• Time required to find T and B cells complementary to the vaccine’s antigen.

• Some antibodies are produced.

• Memory cells are formed and stored.

secondary immune response

• After the second vaccination, the memory cells created after the first vaccine recognize the antigen and proliferation into plasma B

• Large amounts of antibodies are produced.

• Faster response.

• Longer-lasting immunity.

• More than one vaccination is required for immunity to form.

booster vaccines

• Over time, memory T and B cells die.

• Booster vaccines are required to stimulate any remaining memory cells to generate more antibodies and more memory cells.

• Boosters are given much later after a vaccination program.

artificial passive immunity

• The body gains antibodies to the pathogen through injection of antiserum/antivenom produced by another organism.

• No immunological memory is developed.

antivenom

• Used to treat snake bites.

• Contains antibodies created by another organism.

• Antibody treatments increase the number of antibodies at the time of administration but decline shortly after.

• No memory cells developed, therefore no immunological memory.

herd immunity

• When the majority of people in a community are immunized to a disease to prevent the spread of a disease to those who have not been vaccinated.

• The more people vaccinated, the less chance of an infectious agent spreading.

• Larger populations require more individuals immune to a disease.

• More contagious diseases require more people to be immune.

• Protects people who aren’t immune such as those unable to be vaccinated.

• The greater the percentage of the population, the less infected.

non infectious disease

• Illness not caused by a pathogen.

• Causes range from abnormal genes, lifestyle, cancer.

• Eg. cystic fibrosis, cardiovascular disease, Type 1 diabetes.

infectious disease

• Diseases caused by pathogens.

• Pathogens harm the host.

characteristics of pathogens

• contagious: how easily it is transmitted

• virulent: how severe the pathogen is

• Highly contagious and highly virulent are of greatest concern.

emerging diseases

Diseases that have not occurred in humans before, have occurred previously but only affected populations in isolated places, or have occurred throughout history but have only recently been recognized as being caused by pathogens.

re-emerging diseases

Diseases that were once a major public health problem and then declined dramatically in incidence, but then again becoming health problems for many people.

factors influencing the emergence and re-emergence of diseases

• Evolution of organism: resistance to treatment due to changes to the evolution of the pathogen.

• Travel: increased exposure to other populations results in faster spread of diseases.

• Increased exposure to animals (zoonosis): spread of disease from another species to humans.

• Increased population: larger populations lead to increased population densities increasing the likelihood of spread.

• Poor vaccination rates: loss of herd immunity.

• Lack of sanitation and poor hygiene.

• Human behaviour.

• Misuse of antibiotics.

epidemic

Widespread of an infectious disease among a specific population

at a particular time

pandemic

Widespread of an infectious disease to different countries and/or

continents, affecting a greater number of people compared to epidemics

endemic

Constant baseline level in a population (e.g., influenza)

Pathogens Introduced by European Arrival to Australia

• Australia was isolated from other countries.

• The arrival of first convicts and settlers to Australia in 1788 introduced some diseases to Indigenous populations, including: smallpox, syphilis, TB, influenza, measles.

• Resulted in widespread diseases and death.

reasons for susceptibility

lack of immunity of indigenous population, lack of knowledge and experience with European diseases and disruption caused by colonization

Lack of immunity of Indigenous population

• Europeans developed immunity to diseases such as measles and influenza at a young age.

  Indigenous communities were exposed to measles at adulthood. No immunological memory developed, leading to severe reaction.

Lack of knowledge and experience with European diseases

• Indigenous communities responded to diseases differently in their population.

• New diseases meant lack of knowledge to treatment and control.

• No medical treatment

disruption caused by colonization

• Restrictions to food and water due to European settlers.

• Medical practices were disrupted.

• Lead to a decrease in health status, more susceptible to disease and death.

methods to identify pathogens

physical, phenotypic, immunological, molecular

physical method to identify pathogens

identifying using a microscope the structure of the pathogen (virus/bacteria/other).

phenotypic method to identify pathogens

Use of agar plates to allow certain pathogens to grow. The use of certain chemicals on agar allows the growth of certain pathogens, allowing scientists to identify the type of pathogen

immunological method to identify pathogens

diagnosis based on the presence of antibodies or antigens in a person’s serum. Use of ELISA test (Enzyme-linked immunosorbent assay).

ELISA test steps

1. antibodies specific to a certain pathogen are attached to a plate

2. serum added to plate. If serum contains specific antigens, then

they will attach to antibodies.

3. enzyme added. If antigen-antibody complexes form, then the

enzyme will attach.

4. substrate is added to allow the enzyme to change color if an antigen-antibody complex is formed.

molecular method to identifying pathogens

genomic sequencing to identify the pathogen. Use of hybridization-based detection which uses labeled segments of genetic material that are complementary to a pathogen’s genetic material. If a signal is generated, it means the pathogen is present

transmission of diseases

airborne, droplet, direct physical contact, indirect physical contact, fecal-oral transmission

airborne transmission

Sneezing or coughing creates aerosol droplets containing infectious particles (e.g., influenza).

droplet transmission

Respiratory droplets containing pathogens can fall on surfaces; transferred if a person touches eyes, mouth, or nose

direct physical contact

Via touch, exchange of body fluids, sexual contact, mother to baby (e.g., HIV)

indirect physical contact

• Consumption of contaminated food/water, needles.

• Spread also due to vectors such as mosquitoes (e.g., Salmonella, typhoid).

fecal-oral transmission

Pathogens from feces can be consumed by another person via contamination of food or water (e.g., rotavirus causing diarrhea)

controlling disease transmission

prevention, quarantine and isolation, treating

prevention

• Prevent the disease from spreading to other people.

• Keeping pathogen vectors away from human populations.

• Use of PPE

• Disinfectants: applied to non-living materials (e.g., kitchen bench) to kill or slow the growth of pathogens.

• Antiseptics: applied to living tissue to kill or slow the growth of pathogens; includes hand sanitizers.

• Vaccination.

• Education.

quarantine and isolation

Quarantine and isolate to ensure physical distance between infected individuals and the rest of the population.

treating

• Attempting to reduce the impact of disease on humans.

• Antibiotics can be used to break down the cell wall of bacteria and inhibit them from replicating.

• Antiviral drugs prevent the virus from entering or reproducing in host cells.

• Fungicides are used to treat diseases caused by fungi.

antibiotics

• Medication to treat diseases caused by bacteria.

• Can either kill or slow bacterial growth.

• Can be broad-spectrum (affects many different types of bacteria) or narrow-spectrum (only a few specific variants).

antivirals

Medication used to treat diseases caused by viruses.Antiviral drugs prevent the virus from entering or reproducing in host cells.

how do antivirals work

• Preventing entry of the virus by binding to receptors that allow entry

• Inhibiting enzymes involved in reproduction or viral genome-Inhibiting reverse transcriptase

• Stopping newly formed viruses from being released from host cells

• Inhibiting transcription and translation

• Prevent exit of the virus from the cell (therefore reducing spread)

immunotherapy

• Form of medical treatment that alters the immune system’s function.

• Some immunotherapies are designed to increase the action of the immune system, while others suppress it.

• Eg. Antibody therapy using Monoclonal antibodies, Dendritic cell therapy, Cytokine therapy

Antibody Therapy Using Monoclonal Antibodies

• Altering antibodies to treat cancer and autoimmune diseases.

• Laboratory-made proteins that bind to a specific antigen.

• Able to trigger the killing of cancerous cells or self-recognizing cells for autoimmune diseases.

Producing Monoclonal Antibodies

1. Identify and isolate an antigen found on the desired cell, e.g., a cancer cell.

2. Produce a vaccine and vaccinate an animal such as a mouse to produce antibodies against the antigen.

3. Scientists extract B lymphocytes from the spleen of the mice.

4. Extracted B lymphocytes are fused with myeloma cells (rapidly-dividing cancerous human plasma cells) to form hybridomas. This allows B lymphocytes to grow and produce large quantities of antibodies.

5. Hybridomas are selected and are cloned to produce large amounts of antibodies.

6. Antibodies are collected and administered to the same cancer patient.

cancer

• Results from uncontrolled and unregulated replication of cells that then invade other sites of the body.

• Accumulation of mutations in cancer cell’s DNA that allows it to bypass normal checkpoints of the cell cycle.

• Due to carcinogens such as radiation, chemicals, and viruses.

How do Monoclonal Antibodies Work Against Cancer?

• Antibody-dependent cell-mediated cytotoxicity (ADCC)

• Complement activation

• Conjugate monoclonal antibodies

antibody dependent cell mediated cytotoxicity (ADCC)

monoclonal antibodies bind to cancer cells, attracting other

immune cells to destroy.

Complement activation:

monoclonal antibodies bind to cancer cells and interact with

complement proteins to form membrane attack complexes (MAC).

Conjugate monoclonal antibodies:

• monoclonal antibodies with a chemotherapy drug attached and are delivered to cancer cells when antibodies bind to the antigen.

• Targeted and specific therapy compared to radiotherapy/chemotherapy.

Monoclonal Antibodies and Autoimmune Disease

• Monoclonal antibodies can be used to suppress the immune system in autoimmune diseases

• Autoimmune disease results from the body attacking self-cells

• B cells release autoantibodies that target self-cells

• T cells become autoreactive: reacts to self-cells as non-self.

immunosupression

• a reduction in the ability of the immune system to generate an immune response.

• Monoclonal antibodies can inhibit cytokines from binding to autoreactive immune cells.

• They can also bind to autoreactive B and T cells and inhibit their action or stimulate their destruction.

Traditional Cancer and Autoimmune Disease Treatments

• Use of radiation or chemotherapy to treat cancer. However, this causes damage to healthy tissues.

• Use of immunosuppressants to treat autoimmune diseases. However, this leads to immunodeficiency and increased susceptibility to other diseases.

• Monoclonal antibodies are specific to the antigen of the cancer cell or autoreactive cell.