Immune System Flashcards
What are first lines of defence?
Non specfic
1. Skin -oil+ sweat inhibits growth- lysozyme found in sweat and tears digest bacterial cell walls
2. Mucus membranes- found in body openings and resp tract
Mucus trap pathogens
What is immunity and immune response?
Free from burden- organisms ability to recognise and defend against specific pathogens or antigens
Immune response- 3rd line of defence- production of antibodies and generation of specialised lymphocytes against specific antigens.
What is 2nd line of defence?
Non specific
Inflammatory response- release histamine causing bld cells to dilate- bring blood to that area.
Blood vessels become leaky release fluid and WBC
Cause redness and swelling- pus forms( fluid and dead cells)
What white cells are involved in the inflammatory responses?
Macrophages- big eaters engulf pathogens
Neutrophils- engulf bacteria and release chemicals that kill the bacteria and themselves.
Name 2 other forms of 2nd line defence?
Temp response- rises in response to infection
Pathogenic bacteria don’t grow at high temp.
Proteins- complement: kill bacteria by punching holes in memb.
Interferon: protein released by cell infected with virus causes nearby cells to release enzyme preventing reproduction of virus
What is the 3rd line of defence?
Specific- identity of pathogen must be known- response tailored
Involves lymphocytes and antibodies.
List the difference in specific and non specific immunity?
Non specific. Specific
Antigen independent Antigen dependant
Immediate response Lag time between exposure+response
Non antigen specific. Antigen specific
No memory Exposure results in immunologic mem.
What is an antigen?
Any substance capable on inducing an immune response and of reacting with the products of that response eg. Specific antibody or T cell
What is an epitope?
Small part of antigen that interacts with and antibody
An antigen may have several epitopes
Each epitope is recognised by diff antibody ( lock + key)
Found at end of antigen
What are lymphocytes?
Recognise foreign antigens
Produce antibodies
B cells bone marrow T cells thymus circulate in blood and lymph
Name the 2 types of immune response?
Humoral- use B cells to release antibodies
Cellular response - use T cells to attack foreign antigens or the pathogen directly or to trigger the humoral response. (Deal with virus)
Describe the humoral response?
10 million different b lymphocytes each make specific antibody
Huge variety caused by gene coding
B cell meets foreign antigen it binds to receptors of antibody
Stimulates B cell to release antibody into blood
B cell divides producing many clones
Describe the structure of antibodies?
Y shaped quarternary structure
Made of 4 chains joined by disulphide bridges 2 identical light and 2 heavy chains
Peptide bonds between neighbouring amino acids
Belong to group called immunoglobulin
What are the variable regions on antibodies?
2 sections at end of Y arms. Contain antigen binding site. Identical on same antibody but vary from 1 antibody to another.
The constant region-stem and lower parts of Y arms- make up bulk of antigen
What is unique about binding sites?
Has at least 2 antigen binding sites with specific amino acid sequence
Will only bind to a specific antigen- complementary
B cells differentiate into two types of cells, what are they?
Plasma cells - release army of antibodies in response to foreign body
Plasma cells live only a few days
Memory cells - provide immediate response producing antibodies as soon as antigen is reintroduced( very fast response)problem with virus as they mutate
What is the cellular response?
Deal with viruses- pathogens that can enter our cells.
Antibodies cannot cross the cell membrane.
T cells are activated
How are T cells activated?
Special molecules inside a cell report that a pathogen has entered. Let’s T cell know by antigens on surface of cell.
List the 4 types of T cell and their function?
Killer(cytotoxic)- strike pathogen and destroy cell.( cell self sacrificing)
Helper- activate other immune cells- stimulate B cells to make antibod.
Suppressor-stop killer and helper once antigen has been destroyed ( in severe immune disease there is no off switch)
Memory cells- provides immune system with memory of past infection
List the 4 types of antibody- antigen binding?
Agglutination- clump antigens together for phagocytosis
Neutralisation- antibodies bind to toxins blocking active sites
Precipitation- soluble antigens are stuck together to form precipitates
Complement reaction- antibody attach to antigen and attract phagocytes ( flag waving)
What is active immunity?
Lymphocytes activated by antigens on surface of pathogens.
Natural- aquired during infection- memory cells have been created
Artificial- vaccination- also creates a memory
What is passive immunity?
B and T cells are not activated and plasma cells have not made antibodies
Antigen doesn’t have to be encountered for antibodies to be made
Antibodies appear immediately in blood but protection is temporary
What is artificial passive immunity?
Used when rapid immune response is needed eg. Tetanus
Human antibodies from blood Donors who have had tet vaccine
Given a massive dose of these antibodies- no memory cells made so no immunity if exposed again
What is natural passive immunity?
Passed from mum to foetus across placenta. Baby can’t make own antibodies as they haven’t been exposed to antigens.
Colostrum contains IgA remains on surface of baby’s gut wall and passes into blood
