Diseases and Immunity Notes

Pathogens & Barriers

• Pathogen: A disease-causing organism.

• Transmissible diseases are passed on from one host to another.

• Transmission methods:

  • Direct contact: Transfer of body fluids (e.g., HIV).

  • Indirect contact: Via intermediate medium/vector (e.g., mosquitoes).

• Body Defenses:

  • Mechanical barriers: Skin, hairs in the nose.

  • Chemical barriers: Mucus, stomach acid (hydrochloric acid).

  • Cells:

    • Phagocytosis: Engulfing and digesting pathogens.

    • Producing antibodies: Agglutination and signaling for destruction.

Controlling the Spread of Disease

• Preventing the spread involves good hygiene, sanitation, and waste disposal.

• Measures:

  • Clean water supply: Prevents waterborne diseases (e.g., cholera).

  • Hygienic food preparation: Prevents food contamination.

  • Personal hygiene: Reduces transmission of colds and flu.

  • Waste disposal: Reduces pests that act as vectors.

  • Sewage treatment: Removes pathogens from waste.

Active Immunity

• Active immunity involves making antibodies and memory cells.

• Occurs through:

  • Infection with a pathogen.

  • Vaccination.

• Slow-acting but provides long-lasting immunity.

Antigens & Antibodies

• Antigens are molecules on cell membranes.

• Lymphocytes recognize foreign antigens and produce complementary antibodies.

• Antibodies cause agglutination of pathogens and signal phagocytes.

• Initial response takes time; memory cells allow for quicker response upon reinfection conferring immunity.

• Note: Some microorganisms mutate quickly, changing antigens.

• Key Definitions:

  • Antigen: Molecule on cell surface.

  • Antibody: Protein made by lymphocytes to clump antigens.

  • Antitoxin: Protein that neutralizes toxins.

Vaccination Process

• Weakened pathogens or their antigens are put into the body.

• The antigens stimulate an immune response by lymphocytes which produce antibodies.

• Memory cells are produced that give long-term immunity.

  • Role of vaccination in controlling the spread of diseases

Preventing the Spread of Disease (Vaccination)

• Herd immunity: High vaccination percentage protects the entire population.

• Decreased vaccination rates increase the risk of mass infection.

• Vaccination programs can eradicate diseases (e.g., smallpox).

Passive Immunity & Breastfeeding

• Passive immunity: Short-term defense via antibodies from another individual (e.g., mother to infant via breast milk).

• The body does not make its own antibodies or memory cells.

Cholera

• Cholera causes diarrhea, which can lead to death due to loss of water and ions.

• Treated with oral rehydration therapy.

• Vibrio cholerae bacteria cause cholera:

  • Bacteria attach to the small intestine wall and produce a toxin.

  • The toxin stimulates cells to release chloride ions into the intestine lumen.

  • Water moves out of cells into the intestine by osmosis, leading to watery feces.

  • This results in the loss of water and chloride ions from the body.

Pathogens & Barriers

• Pathogen: Something that causes disease.

• Diseases that spread can be passed from one person to another.

• How they spread:

  • By touch: When body fluids are passed (like HIV).

  • Not by touch: Through something else, like mosquitoes.

• Body Protection:

  • Physical blocks: Skin, nose hairs.

  • Chemical blocks: Mucus, stomach acid.

  • Cells:

  • Phagocytosis: Cells eat and digest bad stuff.

  • Making antibodies: Signals to destroy the bad stuff.

Controlling the Spread of Disease

• To stop diseases from spreading, we need to be clean and get rid of waste properly.

• Things we can do:

  • Clean water: Stops diseases from dirty water (like cholera).

  • Clean food: Stops food from getting contaminated.

  • Be clean: Stops colds and flu.

  • Get rid of waste: Reduces pests that spread diseases.

  • Treat sewage: Cleans waste water to remove bad stuff.

Active Immunity

• Active immunity is when your body makes its own defenses (antibodies and memory cells).

• Happens when:

  • You get sick with something.

  • You get a vaccine.

  • It takes time, but it lasts a long time.

Antigens & Antibodies

• Antigens are on the outside of cells.

• Lymphocytes see the bad antigens and make antibodies to fight them.

• Antibodies clump the bad stuff together and tell phagocytes to eat them.

• It takes time at first, but memory cells help fight faster next time.

• Note: Some bad stuff changes quickly.

• Definitions:

  • Antigen: On the outside of cells.

  • Antibody: Made to clump antigens.

  • Antitoxin: Neutralizes poisons.

Vaccination Process

• Weakened bad stuff or parts of it are put in your body.

• This makes your body create defenses (antibodies).

• Memory cells are made for long-term protection.

• Vaccines help stop diseases from spreading.

Preventing the Spread of Disease (Vaccination)

• Herd immunity: When most people are vaccinated, everyone is protected.

• If not enough people get vaccinated, diseases can spread more easily.

• Vaccines can get rid of diseases (like smallpox).

Passive Immunity & Breastfeeding

• Passive immunity: Short-term protection from someone else's antibodies (like from mom to baby through breast milk).

• Your body doesn't make its own