IB Bio Topic 6.3 - Defense Against Infectious Diseases

Skin

the outermost layer of the body. It notably has pores for sweating, hair follicles, and sebaceous glands that produce oils called sebum

Sebum

Oils that keep the skin supple and at a slightly lower pH, making it more difficult for pathogenic bacteria to live on the skin

Mucus Membranes

membranes made up of a surface layer of epithelial cells over a deeper layer of connective tissue. They produce mucus for protection and lubrication

Mucus

A sticky substance that contains glycoproteins and lysozymes (enzymes that attack bacterial cell walls), both of which have antiseptic properties

Clotting Factors

inactive proteins in the blood that are activated individually during a series of several reactions involved in forming blood clots.

Platelets

cell fragments that release chemicals to start the reactions required to form blood clots. They release clotting factors.

Fibrinogen

a soluble, inactive clotting factor in blood that is ultimately converted into fibrin

Fibrin

an insoluble molecule that fibrinogen is converted into by a reaction catalyzed by the enzyme thrombin

Thrombin

An enzyme that catalyzes the reaction that converts fibrinogen into fibrin

Scab

a protective layer formed after a network of fibrin traps red blood cells and platelets. It prevents the entry of pathogens into the exposed skin below it, which is allowed to heal

Thrombus

a blood clot that forms in a vessel and remains in the place where it was formed

Coronary Thrombus

a thrombus that forms in a coronary artery

Specific Immune System

The type of immune system that refers to lymphocytes and antibodies

Non-Specific Immune System

The type of immune system that refers to phagocytes

Leukocytes (White Blood Cells)

any blood cell that has immune function

Phagocytes (Macrophages)

leukocytes that (after chemically recognizing a pathogen) move by amoeboid motion to engulf pathogens and digest them via enzymes secreted from lysosomes

Pathogen

a disease-causing virus or microorganism (viruses, bacteria, protozoans, fungi, prions)

Antigen

any molecule that enters the body and triggers an immune response. They are typically found on the surface of pathogens

Antibody

a large protein with variable regions (produced by the human body) that allow them to recognize and bind to specific antigens

Lymphocytes

leukocytes that produce antibodies in response to immune responses triggered by antigens

B Cells (B Lymphocytes)

a category of lymphocytes notable for having receptors on their surfaces that are essentially antibodies attached as integral proteins such that the antigen binding site points outward

Clonal Selection

Refers to when a specific type of B Cell (activated after binding to an antigen) divides repeatedly via mitosis, resulting in millions of copies of that B Cell that can recognize a specific antigen

Plasma Cells

the type of cell the majority of B Cells become after clonal selection occurs. They make and secrete large amounts of their antibody to be circulated in the blood

Memory Cells

a pool of cells that some B cells become after clonal selection occurs. They remain in the bloodstream and lymph nodes for a long time, allowing for a faster immune response if a specific pathogen invades the human body a second time

Specific Immunity

antibody production in response to an infection from a pathogen that has previously invaded the human body (thanks to memory B cells)

Antigen Presenting Cell (APC)

a special type of leukocyte that traps an antigen and presents it to a T helper cell

T Helper Cell

a type of lymphocyte that activates the immune system after recognizing an antigen trapped by an APC

Killer T Cell

a type of cell that can engulf and kill antigens after a T helper cell activates the immune system

HIV (Human Immunodeficiency Virus)

A retrovirus that notably infects and stops T helper cells from working, greatly hindering the human immune system. Overall, this virus results in a lower amount of lymphocytes in the body.

AIDS (Acquired Immune Deficiency Syndrome)

a range of diseases resulting from HIV lowering the amount of antibodies produced by the human body. It normally only occurs in severely immuno-compromised patients.

Antibiotic

any substance produced by a microorganism (usually saprotrophic fungi) that can inhibit the growth of other microorganisms