Question 1

What are the two types of immune defences in the body?

Accepted Answer

Cell-mediated response using T lymphocytes Humoral response using B lymphocytes

Question 2

What allows for self recognition?

Accepted Answer

The major histocompatibility complex, a cluster of genes on chromosome 6.

Question 3

What does the major histocompatibility complex do?

Accepted Answer

These genes code for MHC antigens that are attached to the surface of body cells, which are recognised as self

Question 4

What are the two types of MHC antigens and what’s the difference?

Accepted Answer

Class 1 MHC antigens are found on the surfaces of almost all human cells, whilst class 2 MHC antigens are found only on macrophages and B-lymphocytes

Question 5

What are antigens?

Accepted Answer

Molecules (usually proteins) that can generate an immune response when detected by the body.

Question 6

Where are antigens found?

Accepted Answer

On the surface of all cells.

Question 7

What are pathogens?

Accepted Answer

Microorganisms that cause disease

Question 8

What are the four types of pathogens?

Accepted Answer

Bacteria, viruses, fungi, and protists.

Question 9

What physical defences are there to pathogens?

Accepted Answer

The skin provides a physical barrier, with a tough outer layer of cells with little water. Tears - lachrymal glands secrete tears which wash away microorganisms from eyes Sebum - secreted by the sebaceous glands containing fatty acids that have an anti microbial action Mucus - produced by goblet cells that trap airborne cells

Question 10

What mechanical defences are there against pathogens?

Accepted Answer

Nasal hairs filter the air that is drawn into the nasal passages Bacteria and other particles trapped in the mucus are swept out of the lungs+ trachea using cilia, tiny hairs that beat with a wave-like motion

Question 11

What chemical defences are there against pathogens?

Accepted Answer

Hydrochloric acid in gastric juice kills most pathogens that reach the stomach. Tears, mucus, saliva and sweat all contain lysozyme which breaks down pathogens by catalysing the hydrolysis of their cell walls.

Question 12

What biological defences are there against pathogens (excluding immune system)?

Accepted Answer

There are natural populations of harmless bacteria living on the skin and mucus membranes that inhibit the growth of many pathogens by competing with them for nutrients.

Question 13

What are antibodies?

Accepted Answer

Antibodies are glycoproteins which belong to a special group of blood proteins known as immunoglobulins.

Question 14

Describe the structure of an antibody.

Accepted Answer

It consists of two pairs of polypeptide chains. Two of the chains are long and are referred to as heavy chains, and two shorter chains are referred to as light chains. These chains are held together by disulfide bridges. It has two identical antigen binding sites (for specific antigens) known as the variable region.

Question 15

What is formed when an antibody binds to an antigen?

Accepted Answer

An antibody-antigen binding site

Question 16

What do antibodies do to A) pathogens B) toxins

Accepted Answer

A)some antibodies act by immobilising the antigens so that the pathogen can be destroyed by phagocytosis B) some antibodies can neutralise the toxins released by pathogens

Question 17

Describe phagocytosis

Accepted Answer

)The phagocyte is attracted to the pathogen by toxins produced by it. It moves towards the pathogen along/up the concentration gradient of toxins. 2) The phagocyte engulfs the pathogen 3) lysosomes in the phagocyte migrate to the newly formed phagosome containing the pathogen 4) Lysosomes release lysozyme into the phagosome, which hydrolyses the bacterium 5) The products of this are absorbed by the phagocyte (6) the phagocyte may wear the antibodies of the pathogen on the cell membrane.

Question 18

What are lymphocytes?

Accepted Answer

White blood cells that recognise and react with antigens

Question 19

What are the two types of lymphocytes?

Accepted Answer

T-lymphocytes and B-lymphocytes

Question 20

Explain how lymphocytes are produced in the body

Accepted Answer

They are developed from stem cells in bone marrow. They migrate to the spleen and lymph nodes and mature. T-lymphocytes initially pass to the thymus where they are activated.

Question 21

Explain the first steps of cell-mediated immunity

Accepted Answer

1) Binding sites on the surface of particular T-lymphocytes form an antigen-antibody complex with the antigens on antigen presenting cells. 2) The T-lymphocytes become activated and start to multiply rapidly, producing many clones which each recognise the same antigen from before as being foreign. 3) These clone differentiates into either i) cytotoxic T-cells ii) helper t-cells iii) memory t-cells iv) regulator t-cells

Question 22

What do cytotoxic t-cells do?

Accepted Answer

They destroy the pathogen by binding to the antigen and releasing the chemical perforin, which creates holes in the cell membranes/walls of pathogens.

Brainscape's Knowledge GenomeTM

Immunity Flashcards

Brainscape's Knowledge Genome^TM