chapter 5 Flashcards
What is an antigen?
Proteins, are molecules that generate an immune response by lymphocyte cells when detected in the body
Antigen variability
pathogens DNA can mutate frequently. If a mutation occurs in the gene which codes for the antigen than the shape of the antigen will change
natural active immunity
following infection and the creation of the bodies own antibodies and memory cells
artificial active immunity
following the introduction of a weakened version of pathogen via vaccine
describe and explain primary immune response
primary: occurs when you are first exposed to pathogen, fewer antibodies will be produced slower, there’s no memory B-cells for that antigen shape
difference between passive and active immunity
in passive immunity antibodies are introduced, does not provide long term immunity, antibodies are not made
in active immunity antigens are introduced, has long term immunity, antibodies are made
secondary immune response
second time you are exposed to pathogen, a large number of antibodies will be made very rapidly as antigen collides with the memory cells it will trigger clonal expansion and there will be a rapid production of plasma cells
Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria becoming a common cause of infection acquired when in hospital.
Some bacteria have alleles for resistance
Exposure to antibiotics is the selection pressure
So high frequency of resistance allele in bacterial population
cytotoxic T-cells
activated by T cells
kills pathogen
by producing protein perforin
causes wholes in the cell membrane
anything can get in or out
causes cell death
monoclonal antibody
an antibody produced by a single clone of B cells
phagocytosis
1- Phagocytes are in the blood and tissues and any chemicals or debris released by pathogens or abnormal cells attract the phagocytes and they will move towards these cells.
2- There are many receptor binding points on the surface of phagocytes. They will attach to chemicals or antigens on the pathogen via these receptors.
3- The phagocyte changes shape to move around and engulf the pathogen.
4- Once engulfed, the pathogen is contained within a phagosome vesicle.
5- A lysosome within the phagocyte will fuse with the phagosome and release its contents.
6- The lysozyme enzyme is released into the phagosome. This is a lytic enzyme which hydrolyses the pathogen.
This destroys the pathogen.
.
7- The soluble products are absorbed and used by the phagocyte
cell mediated response
1- Once a pathogen has been engulfed and destroyed by a phagocyte, the antigens are presented on the cell surface. This is now called an antigen-presenting cell (APC).
2- Helper T cells have receptors on their surface which can attach to the antigens on APC.
3- Once attached, this activates the helper T cells to divide by mitosis to replicate and make large numbers of clones.
4-Cloned helper T cells differentiate into different cells
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 pathogens
vaccine process
Small amounts of weakened or dead pathogens or
are introduced orally or by injection.
Exposure to the antigens activates the B cells to go through clonal expansion and differentiation (clonal selection).
B cells undergo mitosis to make large numbers of cells,
which differentiate into memory cells or plasma cells.
Plasma cells make antibodies
B memory cells divide rapidly into plasma cells when re
infected with the same pathogen to make large numbers of antibodies rapidly
HIV
HIV is transported around in the blood until it attaches to a
CD4 protein on the helper T cells.
The HIV protein capsule then fuses with the helper T cell
membrane, enabling the RNA and enzymes from HIV to enter.
The HIV enzyme reverse transcriptase copies the viral RNA
into a DNA copy and moves to the helper T cell nucleus (this
is why it is called a retrovirus).
Here mRNA is transcribed, and the helper T cell starts to
create viral proteins to make new viral particles
