pathogens - unit 4 AOS 1

Question 1

antigens

Answer 1

• a molecule or part of a molecule which triggers an immune response.
• they are classified as either self or non-self

Question 2

self antigens

Answer 2

• Self markers are located on the surface of cells and mark the cell as being part of the same body so that the immune system doesn’t attack them
• they take the form of MHC markers

Question 3

MHC I markers

Answer 3

• MHC-I is present on all nucleated cells of the body. It contains a site that forms the structural binding site for an antigen. These are what allows cells to be recognised as ‘self’ so they will not be attacked by cells such as natural killer cells or cytotoxic T cells.

Question 4

MHC II markers

Answer 4

• MHC-II is presented mainly on specific white blood cells, including antigen presenting cells (such as macrophages and dendritic cells) and helper T cells. Macrophages and dendritic cells present antigens on their surface on these MHC-II markers, which bind to helper T cells to help activate the adaptive immune response.

Question 5

non self antigens

Answer 5

• Antigens that the immune system reads as foreign and not belonging to the body
• If one is recognised, the immune system will be activated to attempt to eliminate it

Question 6

malfunctions of the immune system

Answer 6

• autoimmune disease: the body reconises self antigens as non-self antigens and initiates an immune response against their own cells

Question 7

pathogens

Answer 7

• A pathogen is a biological agent that causes disease to its host and acts as an antigen, thereby initiating an immune response.
• pathogens can be classified as either cellular or non-cellular

Question 8

cellular pathogens

Answer 8

• pathogens that have a cellular structure and are living organisms
• they can reproduce independently
• includes bacteria, fungi and protozoans

Question 9

cellular pathogen: bacteria

Answer 9

• Unicellular prokaryotes that can infect almost any part of the body and can cause disease through the production of toxins. They release exotoxins and endotoxins

Question 10

cellular pathogen: fungi

Answer 10

• Eukaryotic organisms that include yeasts and moulds and contain long, branching filaments called hyphae.

Question 11

cellular pathogens: protozoans

Answer 11

• Single-celled eukaryotes that can be free-living or parasitic. Protozoa have many different mechanisms of action – for example, some can inhibit nucleic acid synthesis, protein synthesis, and various stages of cellular respiration.

Question 12

non cellular pathogens

Answer 12

• a pathogen that neither has a cellular structure nor exhibits the processes of a living organism.
• they cannot reproduce independlty

Question 13

non cellular pathogen: virus

Answer 13

• An infectious agent composed of genetic material. Viruses are not able to independently reproduce, instead they insert their genetic material into a host’s cell and use the cell to replicate. Viruses can cause disease through the lysis of cells during viral replication, the formation of cancer by affecting gene expression, and the over-stimulation of the immune system leading to organ damage.

Question 14

non cellular pathogen: prions

Answer 14

• Abnormally folded proteins that have the ability to induce normal proteins nearby to become misfolded. They only occur in mammals and affect only the brain and other neural structures. They are currently the only known infectious agents that don’t contain nucleic acids.

Question 15

allergen

Answer 15

• a substance that triggers an immune response despite not being harmful.