Cells Part 3- Immune Responnse, Antibodies, HIV Flashcards
What is an antigen
A foreign protein that stimulates an immune response
Where can antigens be found
The cell surface of an microorganisms
Surface of a virus
Cell surface of tissues/ organ transplant
Free molecules- e.g. toxin
(Cells form other organisms, cancer cells, cells infected by a virus, pathogen)
What are the non-specific defence mechanisms (first line)
Response is immediate and same for all pathogen
First line
- skin- hard for microbes to digest, fatty acids inhibit growth of microorganisms
- mucous membrane - trap microbes
-ciliated epithelium - trachea, bronchioles - sweep mucus
- tears, saliva
What is the second line of defence
Phagocytic white blood cells
What is the third line of defence
Cells mediated response
T lymphocytes
Humorla response
B. Lymphocytes
Describe phagocytosis
A phagocyte recognises the foreign antigen
When the pathogen is englufued into the cell a vesicle forms called phagosome
Phagosomes fuse with another vesicle that’s contains hydrolytic enzymes (lysomes)- forming phagolysosomes
Hydrolytic enzymes hydrolyse th pathogen
Waste material is digested
The pathogens antigen are then present on the surface of the phagocyte to aid activation of specific immunity - antigen presenting cell
What do helper T-cells do
Stimulate b-cells to divide
Secrete interferon and cytokines to stimulate cytotoxic T cells, activate b-cells, phagocytosis
What do cytotoxic t-cells do
Kills body’s abnormal cells
Protein inserts itself into membrane and makes a hole
What do B-lymphocytes do
Specie b cell will have a complementary antibody on its surface
Teach to one another and antigens enter b cells by endocytosis and no wpresente don its surface (APC)
Helper T cell binds to antigen stimulating b cells to divide
Divide by mitosis
Plasma- antibodies
Me both- quicker and higher conc.
What is an antibody
Protein specific to an antigen
Describe the role of antibodies in stimulating phagocytosis
Bind to antigen/ ar markers
Antibodies causes clumping/ agglutination
Attract phagocytes
What is the structure of antibodies
Quaternary structure- 4 polypeptide chains
2 heavy, 2 light
Help by disulphide bonds
Variable region- antigen binding site
What do antibody do
- Agglutination
- Stimulate phagocytosis
- Precipitation
- Prevent attachment of cells
What are monoclonal antibodies
Identical copes of one type of natibody
Made form same type of plasma b-cell
What are the uses of monoclonal antibodies
Immunoassay
Cancer treatment
Reducing rejection
Research
Identify plant disease
Describe the ELISA test
Indirect ELISA test for an antigen-
1. Apply the sample to a surface to which the antigen in the sample will attach
2. Wash the surface several times to remove any unattached antigens
3. Add the antibody that is specific to the antigen you are searching for, and leave it to bind
4. Wash the surface again to remove excess antibody
5. Add a second antibody that bind sot the first antibody, it also has an enzyme attached to it
6. Ad the colourless substrate of the enzyme. The enzyme acts on the substrate to change it to a coloured product
7. Th amount of antigen present present is relative to the intensity of colour that develops
Direct ELISA test
+ $ 1. Add monoclonal antibody to the well which are fixed on the bottom of the well. Ad the sample
and the antigen binds to the antibody
2. Add the second monoclonal antibody, linked to the enzyme, which binds to the antigen
a. Wash and rinse to remove any antibody which is unbound, e.g. as there’s no antigen
3. Add the coloured substrate which is converted by the enzyme into the coloured product
Describe how pregnancy test work
…
How do monoclonal antibodies destroy cancer cells
Specie
Attach to receptors
Block signals that stimulate uncontrollable growth
- indirect
Radioactive drug
An antigen in a vaccine leads to the production of antibodies. Describe the part played by b-lymphocytes
- Antigen binds to/is complementary to receptors on B
lymphocyte; binds to a specific B lymphocyte - Selected B lymphocyte becomes an APC
- B lymphocyte becomes competent/activated; (as a result of TH cells)
- B lymphocytes reproduce by mitosis /B lymphocytes cloned
- Plasma cells secrete antibodies
What is immunity
Acquired characteristic of your immune system that cannot be inherited
What is active immunity
Body make sown antibodies after being stimulated by an antigen
Natural- getting ill, artificial - vaccine
What is passive immunity
Ready-made antibodies
Natural- breastfeeding
Artificial - antibody injections
What are the advantages and disadvantages of active/ passive immunity
Active involves memory cells, passive does not;
Active involves production of antibody by plasma cells / memory cells;
Passive involves antibody introduced into body from outside / named source:
Active long term, because antibody produced in response to antigen:
Passive short term, because antibody (given) is broken down;
Active (can) take time to develop / work, passive fast acting.
Describe how HIV works
- Attachment proteins attach to receptors on helper T cell/lymphocyte;
- Nucleic acid/RNA enters cell;
- Reverse transcriptase converts RNA to DNA;
- Viral protein/capsid/enzymes produced;
- Virus (particles) assembled and released (from cell);
RNA converted into DNA using reverse transcriptase;
Reject ‘messenger’ or ‘m’ before RNA
DNA incorporated/inserted into (helper T cell)
DNA/chromosome/genome/nucleust
DNA transcribed into (HIV m)RNA;
Accept descriptions of transchption
(HIV mRNA) translated into (new) HiV/viral proteins (for assembly into viral particles):
Accept descriptions of translation
Accept named viral protein, eg capsid
Reject viral cells
How does HIV causes symptoms of AIDS
HIV destroys helper cells
B-cells aren’t activated
No long term immunity
Opportunistic infection- infections which would not normally pose a threat
Why don’t antibodies work on HIV
No cell wall in viruses- only protein coat
Hide within cells - cannot reach them
