cell recognition and immunity

What are the four types of pathogen and how do they cause damage?

Bacteria- produce toxins that damage body cells

Viruses- use host cells to replicate before bursting out and destroying cells

Protoctists- take over cells and break them open

Fungi- digest living cells to destroy them and some produce toxins

What are non specific defences?

These act quickly to defend the body but respond in the same way for all pathogens

Specific defences?

These are slower to defend the body but produce a specific response for each pathogen

What are the two types of non specific defences and the two types of specific?

Non specific- physical and chemical barriers and phagocytosis

Specific= cellular response and humoral response

What is inflammation and how is it triggered?

Inflammation consists of swelling, heat, redness and pain at the site of infections or wounds and can be triggered by damaged tissues which release chemical affecting blood vessels either by dialating to increase blood flow and heat to prevent reproduction of pathogens, or blood vessels become more permeable so that they start to leak tissue fluid causing swelling and isolating pathogens in damaged tissue

What are antigens?

Unique molecules usually proteins that can be found on the surface of cells which allow the immune system to distinguish between the bodys own cells and foreign cells

What are 4 examples of foreign cells?

Pathogens, cancerous cells,toxins, cells from other organisms of the same species

What are phagocytes and where are they found?

Are a type of white blood cell that engulfs and destroys pathogens and are found in the blood and body tissue

What is the process of phagocytosis ?

The pathogen releases chemicals that attract a phagocyte (chemotaxis). The phagocyte recognises the pathogen’s antigens as non self which causes the phagocyte to bind to the pathogen. The phagocyte engulfs the pathogen. The pathogen is now contained within a vesicle known as a phagosome. The lysosome containing hydrolytic enzymes called lysozymes fuses with the phagosome to form a phagolysosome. Lysozymes digest and destroy the pathogen. The phagocyte presents the pathogen’s antigens on its surface to activate other cells in the immune system. The phagocyte is then called an antigen presenting cell

What are the two types of lymphocyte and their role and where they are produced?

T lymphocytes or T cells which are produced in the thymus gland and involved in cellular response where they respond to antigens presented on body cells

B Lymphocytes of B cells which mature in the bone marrow and are involved in the humoral response where they produce antibodies found in the body fluid

The three types of T cell and what they do?

1. Helper T cells- they have receptors on their cell surface that bind to complementary antigens on antigen presenting cells. After binding they can form memory cells, stimulate B cells or phagocytes, and activate cytotoxic T cells

2. Cytotoxic T cells- kill abnormal and foreign cells by producing a protein called perforin which makes holes in the cell surface membrane causing it to become freely permeable and causing cell death

3. Memory T cells- provide long term immunity against specific pathogens. They provide a rapid response if the body is re infected by the same pathogen

What are the stages of the cellular response?

Phagocytes engulf pathogens and display their antigens on the cell surface. They are now known as antigen presenting cells. Helper T cells with complementary receptors bind to these antigens. On binding the helper T cell is activated to divide by mitosis to form genetically identical clones

What are the stages of the humoral response?

A B cell with a complementary antibody binds to the antigens on a pathogen. The B cell engulfs the pathogen and presents its antigens on the cell surface membrane to become an APC. Clonal selection- activated T helper cells bind to the B cell causing activation of this B cell. Clonal expansion- the activated B cell divides by mitosis to form plasma and memory clones. The cloned plasma cells produce and secrete the specific antibody which is complementary to the antigen on the pathogen’s surface. These antibodies attach to antigens on pathogens and destroy them. The memory cells circulate the blood and tissue fluid ready to divide if the body is re infected by the same pathogen.

What is the primary immune response?

This takes place when the body is exposed to a pathogen for the first time this response is slow and the infected individual experiences symptoms of the disease

What is the secondary immune response?

This takes place when the body has been exposed to the same pathogen before. This response is much faster and stronger and pathogens are destroyed before any symptoms appear

Describe what happens during the primary immune response?

The production of antibodies is slow after the first exposure to the pathogen. The concentration of antibodies increases slowly. This is because there are very few B cells that are specific to the pathogen’s antigens. It takes time for the B cells to divide into plasma cells to produce the correct antibody so the individual experiences symptoms of the disease. During this process some B cells divide into memory cells to make the individual immune to this disease

What happens during the secondary immune response?

The production of antibodies is much quicker after exposure to the pathogen. The concentration of antibodies increases quickly. This is because memory cells recognise the pathogen’s antigens and quickly divide into plasma cells. These plasma cells secrete larger numbers of antibodies to quickly destroy the pathogen before the individual experiences any symptoms

What are antibodies?

Y shaped glycoproteins made up of four polypeptide chains, two heavy and two light which are held together by disulphide bridges

What are the two regions on an antibody?

Constant region- the same for all antibodies and binds to receptors on cells such as B cells

Variable region- different for each antibody as its shape is complementary to a specific antigen and is the part of the antibody that binds to the antigens

What three roles do antibodies carry out to help destroy pathogens?

Agglutination of pathogens which involves clumping pathogens together to enable easier phagocytosis

Neutralisation of toxins- when antibodies bind to toxins to inactivate them

Preventing pathogens from binding- this is when antibodies bind to pathogens to stop them from infecting body cells

What are monoclonal antibodies?

Antibodies produced from a single clone of plasma cells

What 4 ways can monoclonal antibodies be used?

Diagnosis of disease, treatment of disease, pregnancy testing, detecting certain cancers

What does ELISA test stand for and what its used for and the two types?

Enzyme Linked ImmunoSorbant Assay test uses monoclonal antibodies to detect both the presence and quantity of protein in a sample. Direct tests use one antibody and indirect tests use two

How to carry out an ELISA test?

Add the sample containing the target protein to a well plate where the target protein can attach to the well. Add the antibody that is specific to the target protein. These antibodies will bind to the target proteins attached to the well. Wash the well to remove any unvound antibodies. Add a second antibody that will bind to the first antibody. These secondary antibodies are attached to an enzyme. Wash the well again to remove any unbound secondary antibody. Add a solution containing substrate to the well. The enzyme attached to the second antibody will act on the substrate to cause a colour change. The intensity of the colour change indicates the quantity of protein present.

What is active immunity ?

A type of immunity that develops when the immune system makes its own antibodies after exposure to a pathogen’s antigens. It takes a while to become immune to the disease but it is long term protection because memory cells are produced

What is passive immunity?

A type of immunity that develops when an individual is given antibodies made by a different organism. This method provides immediate immunity to the disease but it is short term protection because the antibodies are broken down and memory cells are not produced.

What is a natural and artificial example of active immunity?

Natural is antibodies made after infection and artificial is antibodies made after a vaccination

What is an example of a natural and artificial passive immunity?

Natural- antibodies transmitted from mother to baby in the womb and artificial is antibodies transfused or injected into individual

What 5 things may a vaccine contain?

Dead or inactive pathogens, weakened pathogen strains, a harmless version of a toxin, isolated antigens from a pathogen’s, genetically engineered antigens

What are the 6 main steps of a vaccination?

1. The vaccine containing antigens is injected into the blood

2. This stimulates the primary immune response to produce antibodies against the pathogen

3. Memory cells capable of recognising these antigens are produced

4. On second exposure to this pathogen memory cells rapidly divide into plasma cells

5. Plasma cells rapidly produce antibodies against the pathogen

6. The pathogen is destroyed before any symptoms are experienced

5 factors that affect how successful a vaccine will be?

Availability, minimal side effects, infrastructure, administration, herd immunity

Why is herd immunity good?

It provides immunity to those that have received the vaccine whilst providing some protection to those who are not vaccinated

6 factors that may prevent the elimination of a disease?

Individual immunity failures, pre immunity infections, pathogen mutations, pathogen variety,pathogen hiding, vaccine objections

What components does HIV have?

Genetic material as two single strands of RNA, enzymes one of which is reverse transcriptase which allows the virus to convert RNA into DNA, capsid which is a layer of protein molecules that surrounds and protects the genetic material, envelope which is an outer layer made of phospholipids, glycoproteins that are attachment proteins that help the virus to bind to host cells

How does HIV replicate?

Attachment proteins on the HIV attach to receptors on a helper T cell. HIV releases its RNA into the helper T cell. Reverse transcriptase converts this RNA into DNA. The viral DNA is inserted into the helper T cell’s genome. The helper T cell’s DNA is translated to make viral proteins. The proteins are used to assemble new HIV particles. Fully assembled HIV particles leave the cell in order to infect other cells.

How does HIV progress and the stages?

Stage 1 is transmission where the HIV is transmitted via direct contact with bodily fluids from an infected individual. Acute infection- once HIV enters the body it rapidly replicates which causes flu like symptoms for 2 to 4 weeks. Stage 3 is the latency period where HIV replication drops to a low level for several years and during this time the individual usually experiences few or no symptoms, this period can be prolonged for many years by ART. Stage 4 AIDS develops after some years, HIV reactivates and destroys helper T cells, as the number of T cells in the body drops over time the immune system begins to fail

What are antibiotics?

Drugs that kill or inhibit the growth of bacteria. They target the bacterial enzymes and ribosomes used in metabolic reactions meaning they do not damage human cells

5 ways antibiotics affect bacteria?

Prevent the synthesis of bacterial cell walls, prevent DNA synthesis, prevent protein synthesis, disrupt protein activity in the cell membrane, disrupt enzyme action

Why do antibiotics not work against viruses?

Because viruses lack cell structures so antibiotics cannot target and disrupt these reactions and antibiotics cannot reach viruses as they invade the organisms’ own cells

How does antibiotic resistance occur?

Genetic mutations occur making some bacteria resistant to an antibiotic. When an infection is treated with antibiotics , resistant bacteria are able to survive. Resistant bacteria reproduce , passing on the allele for antibiotic resistance to their offspring.

Where does the gene for antibiotic resistance reside in a bacterium and what does this mean?

In the plasmids and therefore can be transferred from one bacterium to another in a process called conjugation