Cell Recognition & the Immune System Flashcards
Pathogen def + eg
A disease causing microorganism e.g. bacteria, virus, fungi, parasite
Infection def
The interaction between a pathogen and the body’s defence mechanisms (an invasion of pathogens in the body)
Immunity def
The means by which he body protects itself from infection
Antigen def + eg
(Antibody generator) a foreign protein on the surface of pathogens or other non-self cells that causes an immune response by lymphocytes e.g. bacteria, viruses, fungi, parasites, cancerous abnormal body cells, toxins, transplanted cells
Clonal selection def
When an antigen binds to the cell of a specific T cell clone or when a lymphocyte recognises a foreign molecule and is stimulated to divide
Clonal expansion def
When a T cell clone has the ability to generate into many different cells
Antibody structure
Light chains, heavy chains, hinge region, two antigen binding sites at the ends, variable regions, constant regions
How do antibodies demonstrate the different protein structures?
Tertiary - disulfide bridge
Quaternary - made of more than one (four) polypeptide chains
Passive immunity
Produced by the introduction of antibodies. No direct contact with a pathogen is necessary (eg anti-venom). Immunity is acquired immediately. Antibodies are not produced by the individuals themselves - immunity acquired by by the foetus from the mother when antibodies pass across the placenta to the womb. Antibodies are not replaced when they are broken down, no memory cells are formed, no lasting immunity
Active immunity
Produced by stimulating the production of antibodies by the individual’s own immune system. Direct contact with the pathogen is necessary. Takes time to develop, but generally long lasting. Two types: natural or artificial
Natural active immunity
Individual is infected under normal circumstances
Artificial active immunity
Vaccinations immunisation programme). Induces an immune response without them suffering the symptoms
Vaccination def
Small doses of dead or inactive pathogens or its antigens injected or taken by mouth to induce an immune response and produce memory cells without experiencing symptoms of the disease
Features if a successful vaccination programme
Must be economically available in sufficient quantities to most vulnerable population. Must be few side-effects. Must have available means of producing, storing and transporting the vaccine (technologically advanced equipment, refrigerated transport, hygienic conditions). Must be means of administering the vaccine properly at the appropriate time. Produces herd immunity
Why might vaccinations not eliminate a disease?
People have defective immune systems. Antigen variability (antigen change frequently so antibodies produced no longer match). Too many varieties of a pathogen. Some pathogens hide from the immune system (viruses in the lysogenjc cycle). Individuals object due to ethical, medical or religious reasons.
How are monoclonal antibodies produced?
Mouse is vaccinated to produce antibodies. Antibody-forming cells taken from spleen. Tumour cells grown in tissue culture. Form hybridomas by fusing antibody-forming cells with cultivated tumour cells to stimulate growth. Hybridomas screened for antibody production. Cloned. Monoclonal antibodies isolated for cultivation
Uses of monoclonal antibodies
Pregnancy testing, targeting medication, indirect monoclonal antibody therapy, medical diagnosis
How does phagocytosis lead to presentation of the virus’ antigens?
The vesicle (phagosome) fuses with a lysosome. The virus is hydrolysed by lysozymes. The broken down antigen are then presented on the cell-surface membrane
Why do antibodies only attack certain cells/antigens?
Antibodies have specific tertiary structures. The binding sites and variable regions are complementary to the antigen. The antigen is found on specific cells. Therefore the antibody only binds with these cells
Why can’t ELIZA tests be used to find out if a person has AIDS?
The ELIZA test only shows the number of helper T cells. A person can be HIV-positive but not have AIDS as it doesn’t show the symptoms of the patient
In an ELIZA test what are the reasons for having a control well?
To show the enzyme is causing a colour change. To show that the washing is effective.
If a HIV positive mother gives birth to a baby, explain why the positive result does not prove that they are infected?
Passive immunity would’ve taken place so the solution would have turned blue
How do vaccines lead to the production of antibodies?
A macrophage present antigens on its surface. T cells with complementary receptor proteins binds to the antigen. This stimulates B cells. The B cell divides to form clones or secrete antibodies or presents antibodies on the cell surface membrane
How is HIV replicated after into the human cell?
HIV joins to the host DNA. Reverse transcriptase turns the viral RNA to DNA. HIV proteins are therefore copied in protein synthesis. This is made at ribosomes.
