5 - Immunity Flashcards
Are what some primary defences on the body?
Mucus in the nose and throat - traps pathogens, ciliated epithelial cell ‘wafts’ this up to form phelgm which is coughed out.
Goblet cells - traps particles and pathogens
Stomach acid - pH7 so acidic that enzymes in pathogens are denatured
Skin - acts as a physical barrier, also produced sebum from sebacious glands
Eyes - tears cleanse eyes and contain lysosome, an enzyme
Vagina - acidic, contains lactic acid
Structure of a virus
Envelope protein - has an attachment protein to allow attachment to the host cell for replication
Capsid - nucleic acid protein coat
Nucleocapsid - capsid + viral genome
Viral tegument - cluster of proteins specific to the function of that virus
What are antigens
Antigens are on the cell surface membrane allow cells to identify hemself as self cells to protect against lymphocytes.
What is a pathogen?
A disease causing microorganism
What are the types of pathogen?
Virus
Protist
Fungi
Bacteria
What are the steps to phagocytosis?
1 - phagocyte recognises antigens on pathogen
2 - phagocyte binds to pahtogen
3 - cytoplasm of phagocyte engulfs the pathogen
4 - pathogen contained in a phagocytic vacuole aka a phagosome
5 - lysosomes digest pathogen and absorbs digestive products
6 - phagocyte presents pathogens antigen, becomes an antigen presenting cell
What are the affects of phagocytosis?
Inflammation at the site of infection, the swollen areas contain dead pathogens and phagocytes, this build up is known as ‘pus’, this inflammation is a result of histamine being released
Where are T cells produced and matured
Bone marrow, matured in the thymus gland
The role of T-cells
- Pathogen = engulfed by phagocyte, this is a non-specific process
- phagocyte displays pathogen’s antigen on cell surface
- specific t cell receptor fits onto antigens, the attachment activates T-cells to divide by mitosis, forming clones
- cloned t cells develop memory cells which: stimulate phagocytes to act, stimulate b-cells to produce antibodies and activate cytotoxic t-cells
How do lymphocytes recognise our own cells?
- In foetus: protected by placenta & mother’s immunity
- Any developing lymphocytes that could potentially attack embryo’s self cells are destroyed
- In adults, lymphocyes ate made in the bone marrow and any developing lymphocytes that could potentially attack self cells are destroyed, the resulting lymphocytes mature in the thymus gland
How are T-cells distinguishable from other lymphocytes?
They have a TCR on the cell surface
How do cytotoxic T cells work?
1- Tc cell binds to infected cell on the antigen
2 - Perforin makes holes in infected cells membrane and enzyme enters
3 - Enzyme promotes apoptosis
4 - Infected cell is destroyed.
What is apoptosis?
programmed cell death
What is cell mediated immunity?
responses from cells such as : phagocytes, T-cells, cytotoxic T-cells
What is humoral immunity?
Immunity relating to bodily fluids, for example: B cells in the blood
B Cells/ B lymphocytes ((2))
- Produced in bone marrow
- Covered in antibodies, each have a different antibody on their membrane, different antigens bind to complimentary shaped antigens
Stages of B cell response
1- B cell binds to complimentary antigen
2 - B cell acvtivated to divide by mitosis: creates plasma cells
3 - Plasma cells produce antibodies
4 - Antibodies bind to pathogen and destroy them
5 - Some B cells can develop into memory cells
Memory cells
- Live longer than plasma cells
- Do not produce antibodies
- Circulate in blood/ tissue fluid
- If they encounter the same antigen @ a later date, they rapidly divide into more plasma cells & more memory cells
What are MABs
Monoclonal Antibodies
antibodies produced from a single group of geneticall identical B cells
How are MABs produced
1- Expose mouse to non-self antigens, so it produces B-cells which produce the antibodies required
2- Spleen Cells which produce the lymphocytes are removed
What are the two types of regions in antibodies?
Variable Regions and Constant Regions.
Variable Regions have a unique tertiary structure to bind to complementary antigens, while Constant Regions allow binding to receptors on the immune system.
What is the structure of antibodies?
Made from 4 polypeptide chains: 2 Light Chains and 2 Heavy Chains. The quaternary structure is connected by disulphide bridges.
How many antigens can one antibody bind to at once?
2 antigens
What is the process called when antibodies cause pathogens to clump together?
Agglutination. This process makes it easier for phagocytes to engulf multiple pathogens at a time.
What is the function of antibodies in neutralizing?
Neutralizing toxins released by pathogens
How do antibodies prevent viruses from entering host cells?
By binding to viruses and blocking their entry.
Viruses have protein spikes that recognize and bind to host cell receptors.
What is antigenetic variability?
The formation of different strains of pathogens due to mutations in genetic material. This results in different antigens that are not recognized upon reinfection.
Why is antigenetic variability significant for vaccines?
Commonly varied pathogens have vaccines effective only against the recent strain circulating. This is particularly true for pathogens like Influenza and HIV.
What are the functions of antibodies?
- Agglutination
- Neutralising toxins released by pathogens
- Prevention of Viruses Entering host cells
