2C- Cells and the immune system

describe how a phagocyte destroys a pathogen present in the blood and how this leads to the formation of an APC

• phagocyte recognises antigen on a pathogen

• phagocyte engulfs the pathogen in its cytoplasm forming a phagosome

• lysosomes containing hydrolytic enzymes (lysozymes) fuse with the phagosome and hydrolyse the pathogen

• the phagocyte presents the pathogens antigen on its cell surface to activate other immune cells

give 3 types of cells that can stimulate an immune response

• cells from other organisms/ transplants

• abnormal/ cancerous body cells

• cells infected by a virus

describe the structure of an antibody

what is the role of a disulphide bridge in forming a proteins quaternary structure

joins two different polypeptides together

describe the structure of HIV

• lipid envelope

• don’t need to know about integrase

describe how HIV is replicated

• attachment proteins attach to receptors on helper T cells/ lymphocyte

• nucleic acid/ RNA enters the cell

• reverse transcriptase converts RNA to DNA

• viral proteins, enzymes and capsid are produced

• viral particles are assembled and released from the host cell

define an antigen

• a foreign protein

• that stimulated an immune response

define an antibody

• a protein specific to an antigen

• produced by B cells

describe how to presentation of a viral antigen leads to the secretion of an antibody against the virus

• helper T cells will bind to the antigen on the APC

• Th cells stimulate a specific B cell to undergo clonal selection and divides by mitosis

• this forms many plasma cells that are exact copy’s of the B cell and rapidly produce monoclonal antibody’s

define passive immunity, and what are the two methods to this type of immunity

a type of immunity provided by being given antibody’s made by a different organism

• natural- a baby getting antibody’s from its parent through placenta and breast milk

• artificial- becoming immune from being injected with antibody’s from another organism e.g. antivenom

define active immunity, and what are the two methods to this type of immunity

immunity that is created by your own immune system after being exposed to an antigen and creating its own antibody’s

• natural- immunity after catching a disease

• artificial- through vaccination, being injected with an attenuated form of the virus

contrast active and passive immunity

Active immunity-

• requires exposure to an antigen

• takes a while for protection to develop

• memory cells are produced

• protection is long term

Passive immunity-

• doesn’t require exposure to antigen

• protection is immediate

• memory cells aren’t produced

• protection is short term as antibody’s are broken down

define a cellular immune response

the T-cells and other immune system cells that interact with e.g. phagocytes

define a humoral immune response

B-cells, clonal selection and the production of monoclonal antibody’s

• when a person is bitten by a venomous snake they are injected with a toxin. antivenom is used as a treatment. Antivenom contains antibody’s against the snake toxin. this is an example of passive immunity.

• explain how the treatment with antivenom works and why it is essential o use passive immunity rather than active

• in passive immunity/ the antivenom, antibody’s bind to the toxins antigen causing it to be destroyed

• active immunity would be too slow as there aren’t many B-cells