Immunity Flashcards
(37 cards)
How are cells identified by the immune system
Each type of cell has specific molecules on its surface that identify it
3d tertiary structure enables lots of unique and identifiable shapes to be made
What types of cells and molecules can the immune system identify ?
Non self cells
Detected a response will be triggered to destroy the cell
- Pathogens
- Cells from other organisms of the same species
3.abnormal body cells
4.toxins
Antigens
Protein on the surface of a cell that produces an immune response
Why does immune response occur and what are the two types?
If pathogens get past the chemical and physical barriers and enter the blood then the white blood cells are the second line of defence
Phagocytes - non specific
Lymphocytes - specific
Describe phagocytosis of pathogens(non-specific immune response )
- Phagocyte moves towards pathogen via chemotaxis.
- Phagocyte engulfs pathogen via endocytose to form a phagosome
3.phagosome fuses with lysosome
4.lyzozomes digest pathogen - Phagocyte absorbs the products from pathogen via hydrolysis
Antigen presenting cells APC
Macrophage displays antigen from the pathogen on its surface
- happens after hydrolysis in phagocytosis
- enhances recognition by Th cells which cannot directly interface with pathogens
Cell mediated response - specific
Made in bone marrow
Matured in thymus
1.complementary Th lymphocytes bind to foreign antigen on apc
2. Releases cytokines that stimulate
-Activate Th cells
Which divide by mitosis - replicate making a large number of clones
3.Cloned th cells diffrentiate into different cells
-Activate b cells - humoural response
-Memory cells - copy specific antigen
-Clonal expansion Cytotoxic T cells -
Secrete enzyme perfoin to destroy infected cells
Cytotoxic T cells
Only kill own infected cells
Release chemical called perform
Which puts a hole in membrane sacrifices the cell.
Humoural response - b cells
Made in bone marrow matured in bone marrow
Lymphocytes are white blood cells involved in specific immune responses
- Complementary Th lymphocytes bind to foreign antigen
Presented with a foreign antigen - Release cytokines that stimulate complementary b lymphocytes
- Activates b cells
- Clonal expansion
Differentiate into 2
Plasma b cells - produce antibodies - destroy pathogen - primary immune response
B memory cells -long term immunity
Secondary immune response - produce antibodies faster
Primary and secondary response
Primary - exposed to new pathogen new antigen takes longer for antibodies to produce as you need to go through b cells to find
Few days
Secondary - memory b cellls antibodies created faster
Antibodies
Proteins secreted by plasma cells
Quaternary structure proteins
4 polypeptide chains
2 light chains held together by disulphide bridges
2 longer heavy chains
Rest of molecule known as constant region
- binding site in variable region of light chain have specific tertiary structure to an antigen
How do antibodies lead to destruction of a pathogen
Antibodies help destroy pathogens by agglutination
- Formation of antigen- antibody complex
- Results in aggulatoon which enhances phagocytosis
Definition of vaccine
Explain the principles of vaccination
Injection of antigen from dead microorganism which stimulates formation of memory cells
- Vaccine contained dead pathogen
2.Triggers primary immune response - Memory cells are produced and remain in bloodstream so secondary response is rapid and produces higher concentration of antibodies
4.pathogen is destroys before it can cause symptoms
Types of vaccines
Active and passive
-both involve antibodies
-can be both natural or artificial
Active - weekend form of the pathogen injected into the body to cause
Slower
Acquired immunity
Passive - introduction of antibodies from the outisde source.
Rapid
Natural immunity
-passive natural immunity: antibodies in breast milk
-passive artificial - needle stick infection
-active natural - humoral response to infection
-active artificial- vaccination
Contrast passive and active immunity
Active - direct contact needed with antigen
- memory cells produced Long term protection
- time lag
Lymphocytes produce antibodies
Passive - no direct contact needed with antigen
-uses antibodies from external sources
- immediate response short term protection
- no memory cells produced
Natural and acquired immunity
Natural - passed from the mother to child
Through placenta or breast feeding
Acquired
Injected by a pathogen caused an immune response
Explain how vaccines provide protection to individuals against disease
- specific b lymphocytes with the complementary receptor binds to antigen
-specific T helper cell binds to apc stimaulated b cell - b lymphocytes divide by mitosis to form clones
-some differentiate into b plasma cells which release antibodies - some differentiate into memory cells
- on secondary exposure to antigen b memory cells rapidly divide by mitosis to produce b plasma cells
- these release antibodies faster and a higher concentration
Antigen variability
Mutations in the DNA of the pathogen can lead to the antigen changing shape
Antibodies produce are not complementary
Vaccines are hard to make
Herd immunity
-Vaccinating large proportion of population
-reduces available carries of the pathogen
*Provides protection against those who are not vaccinated for reason .
-Pregnancy
-Too young
- weak immune system
Virus
A cellular
Non loving
Only active once inside the cell
Incase host cell and replicates
Hiv structure
No cytoplasm - can’t carry out any metabolic reaction on its own
-2x rna and viral enzymes surrounded by capsid
- surrounded by viral envelope derived from host cell membrane
Attachment protein - attach to host cell
Can attach to receptor protien
May contain enzymes only work inside the host cell
Hiv
Single stranded RNA- no dna
Reverse transcriptase- enzyme
Retrovirus
Converts RNA BACK to DNA
Method of infection for HIV
- HIV attachment proteins attach to receptors on helper T cell.
- The virus enters the host cell. Hiv uses reverse transcriptase converting RNA TO DNA
- The viral DNA is joined to host DNA . Dna is used to make HIV RNA
- Ribosomes make hiv proteins
5.. new virus particles assemble
Bud off the host membrane
Leads to aids
- Attachment proteins bind to complementary CD4 receptor on Th cells
- HIV particles replicate inside Th cells killing / damaging them
3.AIDS develops when there are too few Th cells for the immune system to function. Can’t activate b / T cells - Pathogens reproduce and release toxins and damage cells
5.
