Topic 5: Cells (immune system) Flashcards
What is the human body particularly vulnerable to
- Pathogens
- Bacteria
- Viruses
- Toxins
Pathogens are anything that cause disease
What defences does the body have
- Non-specific defences (innate immunity)
- Specific defences (Acquired immunity)
Skin, Mucus,secretions(1st)
Phagocytes(2)
Lymphyctes,memory,Plamsa (3)
Define antigens
Antigens are substances or proteins that induces an immune respnse
Name the things that lymphocytes will identify
- Pathogens
- Non-self cells (transplants)
- Cancerous cells (abnormal body cells)
- Toxins (from pathogens)
Contrast Lymphocytes in feotus and in adult cells
- Fetus
The lymphocytes are colliding with self cells because they are rarely infected with pathogens. The lymphocytes that have receptors complementary to the self cells will die or be supressed. - Adult cells
Lymphocytes are found in the bone marrow, where there is only self cells, so lymphocytes that show an immune response to these self cells will undergo apoptosis, so there are none of these in the blood
What do you need to take when you get a transplant
- immunosupressants
Your Lymphocytes will recgonise the cells as non-self
If you maintain lymphocytes which attack self cells, what symptoms do you experience?
Autoimmune disease symptoms
* Fatigue
* Skin problems
* Fever
What happens when your antigens mutate
If a mutation occurs, inj the gene that codes for the shape pf the antigen (or its tertiary structure) any previous immunity is no longer effective, as your memory cells will only have a memory of the old shape.
Are lymphocytes and phagocytes part of the specific, or non-specific response?
- Phagocytes are part of the non-specific response
- Lymphocytes are part of the specific response
Phagocytes attack the same way for any pathogen, therefore non-specific
What are Phagocytes?
A type of white blood cell that undergoes Phagocytosis, by engulfing and digesting foreign material.
What are Macrophages?
A type of Phagocyte that move around in the bloodstream in search of pathogens
Describe Phagocytosis
- Phagocytes are attracted to the chemicals released by foriegn cells, move toward them
- The Phagocytes receptors bind to the antigen of the pathogen, bind if complementary
- This causes the phagocyte to change shape, to engulf the pathogen
- Once engulfed, the pathogen is put in a vesicle called a phagosome
- The phagocytes has the organelle lysosomes in it, which will fuse to the phagosome, releasing lysozymes(lytic enzyme)
- The lysozyme hydrolyses the pathogen, absorbs any soluble products.
- The Phagocyte moves the antigens onto itself, becoming an antigen-presenting cell
Where are T-Lymphocytes and B-Lymphocytes matured
T-Lymphocytes in the Thymus
B-Lymphocytes in the Bone marrow
All lymphocytes are made in bone marrow
State the situations that produce Antigen-Presenting Cells (ACP)
- Infected Body cells will present viral antigens on their surfaces
- A macrophage that has undergone phagocytosis, will have antigens on its surface
- Cells of a transplanted organ
- Cancer cells ( abnormal shaped self- cell antigens
Describe the steps of the cell-mediated response
- You have an ACP
- Helper T-cells (type of T-cells) have receptors which will attatched to the antigens of the ACP if complementary
- Once attatched, the Helper T-cell divide by mitosis, making large number of identical clones which clonal expansion
- The Cloned Helper T-cells differentiate into diff cells by clonal differentiation
- Together this is Clonal selection
ACP (Antigen-presenting cell)
What are the possibilites during clonal differentiation
- Stay as Helper T-Cells
- Stimulate Macrophages
- Become Memory cells
- Become Cytotoxic T-Cells
What do Cytotoxic T-cells do?
Release the protein perforin, which will make a pore in the cell membrane so that any substance cal leave or enter the cell, which will result in (Apoptosis)
Apoptosis is organised cell death
Where can you find antibodies
- Blood
- Tissues
- Tears
- Saliva
- Breast Milk
How many polypeptide chains are antibodies made out of
4 polypeptide chains, forming a Yshape.
Describe the shape of an antibody
2 Heavy chains, which are longer polypeptides,
2 Lighter chains with shorter polypeptides.
Constant region which is the same in all antibodies.
The variable region which is different in all antibodies.
What are the steps of the humoral response?
- Antigen collides with complementary B- cell antibody, the Bcell takes the antigen by endocytosis, and puts it onto its own curface to become an antigen-presenting cell.
- The ACP will collide with a Helper T-cell receptor, to activate the B-cell to undergo clonal expansion and clonal differentiation. (clonal selection)
- They will differentiate into either plamsa cells or memory cells. Plasma cells are responsile for making antibodies. Memory cells are able to rapidly divide into plasma cells upon secondary infection of the same pathogen.
What is the role of memory B-cells
They live for decades and are able to divide by mitosis rapidly to make plasma cells with antibodies, upon secondary infection of the same pathogen.
Define active immunity
Immuity that is acquired through production of antibodies and memory cells, which results in the pathogen being destroyed before symptoms can occur
Primary vs Secondary response
First time ifected = primary response
Second time infected = secondary response
- quicker response because memory cells will release plasma cells with the antibodies quicker
What are the two heavy chains on an antibody joined by
disulfide bonds
How do antibodies lead to the destruction of pathogens
- they have a hing region, making antibodies flexible and able to bind to multiple antigens
- when the antibody binds to the antigen, it forms an antibody-antigen complex
- Because they can bind to multiple antigens, they can clump together called agglutination, making it easier for phagocytes to locate them.
What are some other ways that antibodies destroy the antigens
- serve as markers for phagocytes to find
- if they bind to free toxic proteins, they can change the shape of the active site, so they can no longer cause disease
- by binding to the antigenon bacteria and viruses, they prevent them from attatching to other cells and infecting them.
What are monoclonal antibodies
Identical copies of the same antibody
Name three uses of monoclonal antibodies
- Pregnancy testing
- Medical Diagnosis
- Medical treatment
How do we use monoclonal antibodies
- Scientists add a fluourescent dye to the constant region of the antibody(to allow it to be visualised)
- Then you add the monoclonal antibodies to a group of proteins and it will bind to the correct one
Explain direct monoclonal antibody therapy
Monoclonal antibodies with the specific complementarity to the antigens on cancer cells are produced.
These will be give to a patient, and they will attatched to the receptors on the cancer cells
The antibodies will block the chemical signals that stimulate the uncontrolled cell growth
Explain indirect monoclonal antibody therapy
- You produce the antibodies that have complementarity with the antigens on cancerous cells
- You then attatch therapeutic drugs to the antibodies, and that will allow for the drugs to be sent directly to the cancerous cells and kill them
- This will reduce the harmful side effects of chemotherapy and radiotherapy.
- These are often reffered to as bullet drugs
How is ELISSA test carried out
- Antibody specific to the antigen is bound to the bottom of the well, wash out excess
- Add sample to the well, if antigen present it will bind to the bottom, wash out excess
- Second-antibody specific to tje antigen is added, this antibody is linked with an enzyme that will cuase a colour change reaction whe you add substrate, wash out excess
- Add substrate, the colour change that occurs will depend on the concentration of the antigen.
How do pregnancy tests work
- Pregnant woman will produce hCG
- The hCG will bind to a fluorescent mobile antibody specific to hCG.
- The hCG with the colour will no bind to an immobilised antibody of hCG, so we can visualise it (first window)
- There is another antibody that is specific to the first antibody, to ensure that it is present and there is no false positive.
What is passive immunity
The antibodies are introduced directly into the body. The pathogen doesnt enter the body, no memory cells ro plasma cells.
- Natural Immunity (breastfeeding)
- Artificial Immunity (antibody injections)
No long term gain
Passive (you didnt make them)
What is active immunity
You are infected with the pathogen, therefore you make your own antibodies, memory cells and plasma cells.
- Natural immunity ( when infected)
- Artificial immunity (through vaccination)
Long term advantage
Explain vaccination
- Weakened / dead form of the pathogen
- Exposure to the antigens triggers B-lymhpcytes to undergo clonal selection.
- The B-cell will then undergo mitosis to make large number of cells.
- This is a primary response
Explain antigen variability
Antigens are protiens, which will be coded for by DNA, so if there is a mutation in the gene that codes for the DNA, the antigen shape will change, resulting in all previous immunity to be lost, because all your memory B-cells will only have immunity to the previous shape. This is why vaccinations need to be topped up.
Name the features of HIV
- Attatchement proteins (to enable binding to Helper T-Cells)
- Lipid envelope (made from same as hosts
- Protien Capsid(outer protein coat)
- Viral RNA(core: genetic material (RNA) and enzyme reverse transcriptase, which is needed for viral replication
How does HIV replicate
- HIV travels in the blood, until it attaches with surface protien on a helper-t cell, using its attatchment proteins
- The HIV capsule fuses with Helper-Tcell membrane, enables the RNA and enzyme reverse transcriptase to enter host cell.
- Reverse Transcriptase copies viral RNA into a copy of DNA. The DNA copy moves into the host cells nucleus
- The viral DNA integrates into the host cells DNA, and is transcribed into more viral mRNA. The mRNA will use Helper-Tcell to make viral proteins . This destroys the Helper T-cells
- New viral proteins moe back towards the mebrane , and pinch off to become a new HIV particle.
What is AIDS
AIDS, is when your HIV replicating viruses intefere with the normal functioning of the immune system. Eventually, to many helper Tcells will be destroyed therefore your immune system is compromised and you are more susceptible to infections and cancer.
