Immunology Flashcards
What is an Antigen presenting cell (APC)
Any cell which has a non self antigen on the surface;
Infected body cells
Phagocytes which have engulfed and destroyed a pathogen
Cells of a transplanted orgam
Cancer cells
T lymphocytes (T cells)
All lymphocytes are made in the bone marrow but T cells mature in the thymus
The cell mediated response focuses on T cells and body cells, it is specific as T cells respond to antigens
Cell mediated response
1) Once a pathogen has been destroyed by a phagocyte the antigens are presented on the cell surface and this is now an APC
2) T helper cells have receptors on their surface which attach to the antigens on the APC
3) T helper cells once attached divide by mitosis to make large numbers of clones
4) Cloned T helper cells can differentiate into different cells:
- Stay as T helper and activate B lymphocytes
- Stimulate phagocytes
- Memory cells
- T killer cells
T killer cells
Release perforin which embeds itself in the cell surface membrane meaning that any substances can enter or leave the cell, leading to cell death
Phagocytosis
1) Pathogen enters body and begins harming the cell either through releasing toxins or direct damage
2) Body cells release a chemical ie histamine which attracts phagocytes and they move towards the cell - chemotaxis
3) There are many receptor binding points on the surface of phagocytes- They attach to antigens on the pathogen via these
4) The phagocyte changes shape to engulf the pathogen, once engulfed the pathogen is contained within a phagosome vesicle
5) A lysosome within the phagocyte will fuse with the phagosome forming a phagolysosome. The lysosome enzyme is released and this is a lytic enzyme which hydrolyses the pathogen
6) This destroys the pathogen. The soluble products are absorbed and used by the phagocyte
Humoral response
1) Antigens in the blood collide with their complimentary antibody on a B cell, The B cell takes in the antigen via endocytosis and presents it on its cell surface
2) B cell collides with a T helper cell and goes through clonal expansion and differentiation, undergoes mitosis to make large numbers of cells - become either plasma cells or B memory cells
3) Plasma cells make antibodies
4) B memory cells divide rapidly into Plasma cells when reinfected with the same pathogen therefore they make large numbers of antibodies rapidly
This means that the pathogen is destroyed before any symptoms can occur which is active immunity
What is agglutination
Antibodies are flexible and can bind to multiple antigens to clump them together
This makes it easier for phagocytes to locate and destroy the pathogen
Active immunity
Immunity created by your own immune system following exposure to a pathogen or its antigen
Natural active immunity occurs following infections and the creation of the bodies own antibodies and memory cells
Artificial active immunity occurs after a vaccine
HIV replication
Attaches to attachment protein on T helper cell
The capsid fuses with the T helper cell membrane which enables the RNA and enzymes to enter
The enzyme reverse transcriptase copies the viral RNA into a DNA copy and moves to the T helper cell nucleus
ELISA test
1) Add test sample to base of the beaker
2) Wash to remove any unbound test sample
3) Add an antibody complementary in shape to the antigen you are testing
4) Wash to remove any unbound antibody
5) Add a second antibody which is complimentary in shape to the first antibody and binds to the first but the second has an enzyme attached to it
6) The substrate for the enzyme which is colourless is added. This substrate produces coloured products in the presence of the enzyme
Explain how HIV affects the production of antibodies when aids develop in a person
Less antibodies produced
as HIV destroys T helper cells
so fewer B cells activated
