Chapter 12 - Communicable diseases

Communicable diseases

diseases that can be passed from one organism to another, of the same or different species

Pathogens

microorganisms that cause disease

Vectors

a living or non-living factor that transmits a pathogen from one organism to another

Bacteria

small, single-celled prokaryote

Gram positive

bacteria with cell walls that stain purple-blue with gram stain

Gram negative

bacteria with cell walls that stain red with gram stain

Antibiotics

a chemical or compound that kills or inhibits the growth of bacteria

Virus

non-living, parasitic pathogen that can cause diseases in organisms

Bacteriophages

viruses that attack bacteria

Parasites

an organism that lives on or in a host organism and feeds at the expense of the host

Protista

biological kingdom containing unicellular eukaryotes

Fungi

biological kingdom containing yeasts, moulds and mushrooms

Inoculation

where the pathogen is transferred directly from one individual to another by a break in the skin

Ingestion

where a pathogen is eaten through contaminated substances or hands

Fomites

where a pathogen is indirectly transmitted through inanimate objects (e.g. socks, bedding)

Callose

large polysaccharide deposited in plasmodesmata and between cell walls and membranes in response to infection, blocking the flow so pathogens cant spread

Chitinases

enzyme that catalyses the degradation of chitin

Glucanases

enzymes made by some plants that break down glucans

Mucous membranes

membranous linings of body tracts that secrete a sticky mucus

Inflammation

biological response of vascular tissues to pathogens, damaged cells, or irritants, resulting in pain, heat, redness and swelling

Mast cells

releases histamines and cytokines in damaged tissues

Histamines

makes blood vessels dilate, causing localised heat, redness and swelling. it raises temperatures, preventing pathogens from reproducing

Cytokines

attracts phagocytes (specialised WBC) for phagocytosis of pathogens

Phagocytosis

where phagocytes recognise non-self cells, engulf them within a vesicle called a phagolysosome

Phagosome

the vesicle in which a pathogen or damaged cell is engulfed by a phagocyte

Phagolysosome

when a phagosome fuses with a lysosome

Major histocompatibility complex

a glycoprotein marker used to distinguish self cells from non-self cells

Antigen presenting cell

cells that display foreign antigens combined with MHCs on the cell surface

Opsonins

chemicals that bind to antigens on pathogens, making them more easily recognised by phagocytes

Antigens

molecules on the surface of a pathogen/non-self molecules produced by a pathogen that triggers an immune response and causes antibody production

Antibodies

Y-shaped glycoproteins made by B cells of the immune system in response to the presence of an antigen

Specific immune system

when the immune system ‘remembers’ an antigen after an initial response, leading to an enhanced response to subsequent encounters

Immunoglobulins

Y-shaped glycoproteins that form antibodies

Antigen-antibody complex

the complex formed when an antibody binds to an antigen

Agglutinins

chemicals (antibodies) that cause pathogens to clump together for easy mass phagocytosis

B lymphocytes

lymphocytes which mature in the bone marrow. involved in the production of antibodies

T lymphocytes

lymphocytes which mature in the thymus gland, and both stimulates B lymphocytes and directly kill pathogens

T helper cells

T lymphocytes with CD4 receptors on their cell surface membrane which bind to antigens on APCs and produce interleukins

Interleukins

a type of cytokine produced by T helper cells

T killer cells

T lymphocytes that destroy pathogens carrying a specific antigen using the chemical perforin

Perforin

perforates cell membranes of pathogens

T memory cells

T lymphocytes that remain in lymph nodes to respond rapidly if the same type of pathogen invades again

Immunological memory

the ability of the immune system to respond more rapidly and effectively to pathogens that have been encountered previously

T regulator cells

slows down and stops the immune reaction after 1 week through the action of interleukins

Autoimmune response

when the immune system acts against its own cells and destroys healthy tissue in the body

Plasma cells

B lymphocytes that produce antibodies to a particular antigen

B memory cells

produces and secretes antibodies into the bloodstream - only lives for a few days

Clonal selection

when the APC finds the complementary lymphocyte, and the T cell is activated and physically joins with the receptor

Clonal expansion

rapid multiplication and differentiation

Primary immune response

the initial response to a newly encountered antigen

Secondary immune response

the response to a previously encountered antigen

Autoimmune disease

A condition or illness resulting from an autoimmune response

Natural active immunity

immunity which results from the response of the body to the invasion of a pathogen

Natural passive immunity

The immunity given to an infant mammal by the mother through the placenta and the colostrum

Artificial active immunity

Immunity which results from exposure to a safe form of a pathogen e.g. by vaccination

Artificial passive immunity

immunity from the administration of antibodies from another animal against a dangerous pathogen

Vaccine

safe form of an antigen, injected into the bloodstream to provide artificial active immunity against a pathogen with the antigen

Epidemic

when a communicable disease spreads rapidly to a lot of people at a local or national level

Pandemic

When a communicable disease spreads rapidly to a lot of people across a number of countries

Penicillin

the first widely used safe antibiotics derived from a mould

Penicillium notatum

Pharmacogenomics

A field of medicine that investigates how a person’s genetic makeup may affect how their body processes certain medications

Selective toxicity

The ability to interfere with the metabolism of a pathogen without affecting the cells of the host

Antibiotic resistant bacteria

Bacteria that undergoes mutation to become resistant to an antibiotic and then survive to increase in number

MRSA

Mutated strain if the bacterium Staphylococcus aureus that is resistant to the antibiotic methicillin

C. diffic

A species of Gram postitive bacteria that is resistant to most antibiotics

direct transmission

where the pathogen is transferred directly from one individual to another by direct contact, inoculation, ingestion

indirect transmission

where pathogen travels from one individual to another indirectly through fomites, droplet and vectors