Immunity Flashcards
What is an antigen?
Molecules that are usually proteins that generate an immune response
Describe phagocytosis
•Pathogen is engulfed by phagocyte
•antigen gets enclosed into a phagosome
•lysosomes fuse with the phagosome releasing hydrolytic enzymes to break done pathogen
•phagocyte is now antigen-presenting cell
What is an antigen presenting cell?
Body cells that present the antigens of pathogens on their cell surface membrane. E.g phagocytes after phagocytosis or body cells that are infected by a virus.
What are T Helper cells?
A type of T lymphocyte that have a receptor complimentary to the antigen on the pathogen. They release chemical signals that activate phagocytes to come and cytotoxic T cells to kill infected cells.
What do cytotoxic T cells do?
Kill abnormal and foreign cells
Describe the process of humoral response
The antigen presenting cells is found by the B-lymphocyte with a complimentary receptor bind to the antigen and the T Helper cell activates the B cell to divide by mitosis. Clones of these become plasma or memory cells.
What are plasma cells? How are they different to memory cells?
Plasma cells release antibodies that are specific to the foreign antigen. They are short lived, unlike memory cells that are long lived.
What are memory cells?
They are long lived clones of B cells that bring about the secondary immune response and give us long term immunity.
What is clonal selection?
The B cell with the complimentary receptor binding with the antigens
What is clonal expansion
B-lymphocytes divide by mitosis (stimulated by t helper cells) to form clones of B cells become plasma cells or memory cells.
What is the secondary response?
Clonal selection and expansion is faster and so antibodies are produced faster and in a greater number. This faster response due to antibodies bring out immunity.
What is a monoclonal antibody
A protein produced by a clonal B lymphocyte specific to an antigen. Lots of one type of antibody
Describe cell-mediated response
•A T-Helper cell with complimentary receptor binds to antigen on an antigen-presenting phagocyte
•T-Helper cell releases chemical (interleukin) to attract more phagocytes to come
Describe the structure of an antibody
Constant regions that are the same across all antibodies, and variable regions that have unique tertiary structure with a binding site on the end
Tertiary structure
Further folding of coiled chain of amino acids
How are all antibodies specific?
They have specific binding sites
unique tertiary structure that only one antigen with the complimentary structure can bind to.
Each antibody has a specific amino acid sequence
How do antibodies kill pathogens?
The two binding sites can bind to two pathogens at the same time. Pathogens can get clumped together known as agglutination. Phagocytosis then occurs to destruct the pathogens.
What process describes the clumping together of pathogens?
Agglutination
What is antigenic variability
Some pathogens change their surface antigens (due to changes in genes). If you get infected by the same pathogen a second time, the memory cells initially produce produced will not recognise the antigens. the primary response then gets carried out again and take slower if you get ill again.
What is a vaccine?
An injected form of a pathogen dead or weakened ( attenuated ) to produce memory cells
How do vaccines work?
Vaccines contain antigens from pathogens.
T cells with complementary receptor binds to the antigen. T cell stimulates B cell with the complementary antibody on its surface.
B cell secretes large amounts of antibodies by dividing to form clones all with the same antibody
Passive immunity vs active
Active involves memory cells and production of antibody from our own immune system. Passive involves antibodies from a different organism, not your own.
What is a retrovirus?
Virus that contains RNA rather than DNA.
How does HIV progress into AIDS?
HIV kills T helper cells so the immune system cannot give an effective response. T-helper cells reach a critically low level.
Why are antibiotics ineffective against a virus?
Antibiotics target ribosomes and interfere with bacteria metabolic reactions. viruses don’t have these so they don’t get affected
How does HIV reproduce?
Attachment protein attaches to receptor molecule on the cell membrane of the host helper T cell.
Capsule releases RNA into host cell cytoplasm.
Reverse transcriptase makes RNA strand into a DNA copy
DNA joins to host cells DNA
Host cell enzymes make viral proteins from the viral DNA found in human DNA
Viral proteins are assembled into new viruses which bud from the cell and go on to infect other cells.
What does reverse transcriptase do?
Make a complementary strand of DNA from the viral RNA template
What are the functions of helper T cells?
Releases chemicals that attract phagocytes
Activates B cell to divide by mitosis to form clones
Attracts cytotoxic T cells
How does HIV replicate in our T H cells?
The attachment proteins bind to the cell surface membrane of the host cell and the RNA and reverse transcriptase are injected inside where reverse transcriptase creates a viral DNA strand from the viral RNA. The viral DNA joins a host cell DNA and the host cell DNA replicates viral RNA and proteins
How can monoclonal antibodies be used to treat cancer?
An antibody is attached to an anticancer drug. The binding site of the antibody is complementary to the tumour cells antigen so they bind together and the drug breaks down the tumour cells.
