IB Biology SL - Topic 6: The Immune System

Bacteria

Prokaryotes that divide via binary fission; can cause food poisoning, ear and eye infections, cholera, and diarrhea

Fungi

Eukaryotes that reproduce via spores; can cause athlete's foot, allergic reactions, and respiratory problems

Viruses

Acellular and non-living organisms that need a host to carry out the functions of life; can cause flu, HIV, smallpox, measles, common cold, herpes, ebola, etc

Protozoa

Simple parasites; can cause malaria, leishmaniasis, and toxoplasmosis

Methods of Transmission

Inhaled droplets, direct contact, bodily fluids, animal vectors, ingestion

Mucous Membranes

First line of defense; trap invaders, pH is not favorable to pathogens, lysozome enzymes break down pathogens, natural organisms provide competitive exclusion

Skin

First line of defense; continuous and tough, dry, pH is not favorable to pathogens, lysozomes in sweat break down pathogens, natural organisms provide competitive exclusion

Platelets

Solid parts of the blood that aid in blood clotting

Clotting Factors

Proteins that help to stop bleeding via creating blood clots

Fibrin

Protein which forms a mesh of fibers across open wounds; activated after outside exposure

Thrombin

Chemical that converts fibrinogen (soluble in blood) to fibrin (not soluble)

Atherosclerosis

Degenerative disease where fibrous tissue grows in the damaged areas of artery walls; build-up of cholesterol forms plaques which leads to a loss of elasticity, narrowing the lumen and restricting blood flow

Coronary Thrombosis

Blood clot forming in the blood vessels of the heart, caused by the rupturing of built-up plaque

First Line of Defense

Non-specific; skin, mucous membranes, secretions of skin and mucous membranes

Second Line of Defense

Non-specific; phagocytic leukocytes, antimicrobial proteins, inflammatory response, fever

Third Line of Defense

Acquired and specific; lymphocytes, antibodies, memory cells

Histamine

Chemical produced by leukocytes (basophils and mast cells) which aids in the inflammatory response

Inflammatory Response

Hives, itching, capillary permeability; overreaction may cause allergies

Antigen

Molecule recognized as foreign by the immune system, being treated as a foe; outlines the surface of cells

Self Marker (MMC)

Labels the body's cells as 'friend' and are tolerated by the immune system

Phagocytic Leukocytes

White blood cells which attach to pathogens' cell surfaces and engulf them

Chemotaxis

Movement in response to chemicals

Phagosome

Vesicle within the phagocyte which forms when the pathogen has been engulfed; contains it and lysosomes deposit enzymes to break it down

Phagocytosis

The process of endocytosis utilized by phagocytes

Zoonosis

A disease or infection that is naturally transmissible from vertebrate animals to humans; e.g. ebola and salmonella

Humoral Response

Process in the third line of defense in which antibodies are produced

Helper T-cells

Cells to which antigens on the surface of phagocytes (after phagocytosis) bind to; activates B-cells

B-cells

Cells which divide to produce plasma and memory cells

Plasma Cells

Produce antibodies specific to an invader

Memory Cells

Remember invaders for future recognition; allows for the development of immunity, particularly in vaccination

Cytokines

Chemicals used for cell activation between Helper T-cells and B-cells

Antibodies

Immunoglobulins; proteins produced by plasma cells which mark invaders due to their antigens, triggering an immune response

Paratope

Part of the Y-shaped antibody; variable and specific to an antigen's epitope

Precipitation

Makes soluble antigens insoluble, aiding in their elimination via phagocytosis

Agglutination

Links cell-bound antigens together, causing clumping which aids in elimination via phagocytosis

Neutralization

Marks dangerous parts of the pathogen (e.g. exotoxins) which aids in elimination via phagocytosis

Inflammation

Triggers histamine release, increasing immune mobility which aids in elimination via phagocytosis

Complement

Protein perforates the cell membrane and leads to cell lysis (breaks open the cell, killing the pathogen)

Active Acquired Immunity

Production of own antibodies due to natural or artificial (vaccine) exposure

Passive Acquired Immunity

Ready-made antibodies due to maternal antibodies or other sources (e.g. rabies treatment)

Innate Immunity

Genetic immunity

Acquired Immunity

Development of immunity through the third line of defense

Vaccination

Allows for individuals to become immune to a disease without experiencing it

Primary Immune Response

Initial immune response to a vaccine; body is presented with inactive virus or antigens

Antibiotics

Medicine which combats prokaryotic bacteria by disrupting structures and metabolic pathways; e.g. penicillin

Penicillin

Antibiotic derived from the fungus S. aureus; discovered by Fleming and supported by Florey & Chain

HIV

Human Immunodeficiency Virus; gradually attacks the immune system by damaging Helper T-cells; can lead to AIDS

AIDS

Caused by HIV; the immune system is too weak to fight off infection, eventually leading to death by opportunistic diseases; diagnosed when there is 200 Helper T-cells per mm3