2.4 Cell recognition and the immune system

Question 1

Antigens

Answer 1

Molecules that can generate an immune response when detected by the body. Usually found on the surface of cells. Foreign antigens are those not normally found in the body

Question 2

Pathogens

Answer 2

Organisms that cause disease (bacteria, viruses and fungi). All have antigens on their surface

Question 3

Abnormal body cells

Answer 3

Cancerous or pathogen-infected cells have abnormal antigens on their surface, trigger an immune response

Question 4

Toxins

Answer 4

Poison molecules, some are produced by bacteria

Question 5

Cells from other individuals of same species

Answer 5

Cells from another person also have antigens, some antigens will be different to our own. These trigger an immune response

Question 6

Phagocytosis (Immune Response Step 1)

Answer 6

1. A phagocytes is a type of white blood cell that carries out phagocytosis
2. Phagocytes recognises foreign antigen, cytoplasm then moves around it and engulfs it
3. Pathogen contained in phagocytic vacuole, a lysosome fuses with vacuole and lysozymes break down pathogen
4. Phagocytes presents the pathogen’s antigen, acts an an antigen-presenting cell

Question 7

T-Cells (Immune Response Step 2)

Answer 7

1. Type of white blood cell, has receptor proteins on surface that bind to complementary antigens presented by phagocytes
2. Helper T cells release chemical signals and stimulate phagocytes, and activate B-cells
3. Cytotoxic T cells kill abnormal and foreign cells

Question 8

B-Cells (Immune Response Step 3)

Answer 8

1. Type of white blood cell covered in antibodies
2. Each one has a different shaped antibody
3. Binding of complementary antigen and substances released from helper T-cells, activate B-cells (clonal selection
4. Activated B-cell divides into plasma cells

Question 9

Antibody production (Immune Response Step 4)

Answer 9

1. Plasma cells are identical to B-cells, they secrete loads of antibodies specific to the antigen, called monoclonal antibodies
2. Bind to antigens on surface of pathogen, agglutination occurs
3. Phagocytes then bind to antibodies and phagocytosis of multiple pathogens happens

Question 10

Antibody

Answer 10

Proteins, made of chains of amino acids, specificity depends on variable regions that form antigen binding site. All antibodies have same constant region

Question 11

Cellular response

Answer 11

The T-cells and other immune system cells that they interact with

Question 12

Humoral response

Answer 12

B-cells, clonal selection and the production of monoclonal antibodies from the humoral response

Question 13

Primary immune response

Answer 13

When an antigen enters the body for the first time and activates the immune system. Response is slow because not many B-cells to make antibody needed. After being exposed to antigen, both T and B cells produce memory cells

Question 14

Memory T-cells

Answer 14

Remember the specific antigen and will recognise it a second time around

Question 15

Memory B-cells

Answer 15

Record the specific antibodies needed to bind to the antigen

Question 16

Secondary immune response

Answer 16

If same pathogen enters again, immune system will produce a quicker, stronger immune response. Clonal selection happens faster. Secondary response often gets rid of pathogen before you begin to show symptoms

Question 17

Active immunity

Answer 17

Type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen. Natural or artificial (vaccine containing a harmless antigen dose)

Question 18

Passive immunity

Answer 18

Type of immunity from being given antibodies made by a different organism. Natural (baby receiving immunity from moms antibodies), artificial (becoming immune after being injected with antibodies from someone else)