Immune Cells

Question 1

Pathogens

Answer 1

Microorganisms that cause disease

Produce toxins & kill cells, damage tissues

Question 2

Antigen

Answer 2

Foreign proteins on surface of cells that can generate an immune response

Specific in shape & size - diff species have their own unique antigen shape

Question 3

Phagocytes

Answer 3

Type of WBC found in blood & tissues

First responders in an immune response

E.g. macrophage

Engulf & destroy pathogens with enzymes

Question 4

Phagocytosis

Answer 4

Phagocyte recognises non-self cell by its antigens

Cytoplasm wraps around cell

Cell is taken in by endocytosis

Cell contained in a vesicle called a phagosome

Antigens of pathogen sent to suface of cell & attached to MHC proteins to be presented (APC)

Lysosomes fuse with phagosome + pathogen digested by enzymes

Question 5

T helper cells

Answer 5

Type of WBC

Receptor proteins bind to complimentary antigens presented by phagocytes

Once antigen-antibody complex is formed, t cell is activated

Activated T helper (TH) cells release cytokines which stimulate phagocytes and cytotoxic T cells to kill

Chemicals also activate B cells which secrete antibodies

Question 6

Cytotoxic t cells

Answer 6

Type of WBC

Receptor proteins bind to complimentary antigens presented by infected cells

Once an antigen-antibody complex is formed and cytokines from T helper cells are received, cytotoxic T cell is activated

Cytotoxic T cells release perforin which makes holes in the infected cells membrane and kills it

Question 7

B cells

Answer 7

Type of WBC

Covered in antibodies

Each B cell has different shaped antibodies and so binds to different antigens

Once a B cell antibody binds to a complimentary antigen & receives cytokines from a T helper cell, it becomes activated and divides by mitosis into plasma cells = clonal selection

Question 8

Antibodies

Answer 8

Activated B cells divide by mitosis into plasma cells and produce many identical monoclonal antibodies (all specific to the antigen first detected)

Variable regions have specific primary structure which lead to a tertiary structure complimentary to a specific antigen

Antigen-antibody complexes only formed with this specific antigen

Question 9

Antibody parts

Answer 9

Binding sites

Variable region

Constant region

Heavy chains

Light chains

Hinge region

Disulphide Bridge

Question 10

Antibodies 2

Answer 10

2 binding sites to bind to 2 pathogens at same time

Allows for agglutination

Phagocytes bind to the antibodies and phagocytise manh pathogens at once