Flashcards in Immune System Deck (60):
What is the immune system?
A complex system responsible for distinguishing host cells from foreign material - in order to protect against infections.
What structures enable the immune system to recognise something as foreign?
1) MAMP (microbe-associated molecular patterns)
The 7 stages of the infectious disease process?
1) Transmission or spread of bacteria
2) Entry into a body and colonisation - infection
3) Obtains the essential nutrients for growth
4) Avoids the host's defence mechanisms (innate and adaptive)
5) Spreads within the host or to other hosts
6) Effects the host
7) Host response
What are the 2 types of the immune system's defence mechanisms?
What are the 3 differences between the innate and adaptive defence mechanisms?
1) Innate mechanisms target a broad range of pathogens whereby adaptive mechanisms target specific pathogens.
2) Innate mechanisms are rapid (minutes, hours) whereas adaptive mechanisms take longer (days)
3) Innate mechanisms do not develop memory whereas adaptive mechanisms do develop memory
What are the 9 immune tissues called?
2) Tonsils and adenoids
3) Lymph nodes (in the neck, armpits and groin)
4) Lympathic vessels
7) Peyer's patches (small intestine)
9) Bone marrow
4 components of innate immunity?
1) Barriers = a) Physical & b) Chemical barriers
2) Antimicrobial agents
3) Specialised cells = a) Natural Killer cells & b) Phagocytes
4) Inflammation & Fever
What are the 5 physical barriers?
3) Respiratory Tract
4) Gastrointestinal Tract
5) Genitourinary Tract
What 5 things makes the skin a physical barrier?
3) Low pH
4) Commensal bacteria
5) Shedding of the skin
What makes the eyes a physical barrier?
Tears (contain lysozyme)
What 2 things make the respiratory tract a physical barrier?
2) Ciliated epithelium
What 5 things make the gastrointestinal tract a physical barrier?
1) Stomach acid
2) pH change in the duodenum
3) Normal flora
4) Mechanical removal (vommiting)
What 4 things make the genitourinary tract a physical barrier?
1) Passing of urine
2) Urine acidity
3) Vaginal secretions
What do the chemical barriers involve:
Cell-signalling molecule = cytokines (e.g. interferons)
How do cytokines (e.g. interferons) provide an immune response?
They will carry out an immune response against viruses.
1) A cell is infected with a virus
2) The infected cell produces and secretes interferons
3) The interferons will bind to the receptors on nearby cells
4) This triggers the anti-viral response inside the infected cell
5) Infected cell is left undamaged
What are the 2 types of natural killing cells?
1) White blood cells
2) Tissue-dwelling cells
What do the natural killing cells do?
1) Recognise INFECTED cells
2) Kill the infected cell
3) The natural-killing are left undamaged.
What 2 types of cells can carry out phagocytosis?
1) White blood cells
2) Tissue dwelling cells
What occurs in the process of phagocytosis?
1) The microbe attachers to the phagocyte (via a non-specific receptor)
2) A phagosome forms around the microbe.
3) The microbe will fuse with the lysosome in the phagosome.
4) The digestive enzymes are released from the lysosome.
5) The microbe is digested and microbial agents are released from the phagocyte.
What other cells are involved in innate immunity and why?
Polymorphonuclear cells (basophils, neutrophils eosinophils)
1) The first to arrive at the site of infection
2) They contain granules - that allow them to chemically attach microbes.
When does inflammation occur?
Inflammation will occur when a cell experiences traumas (e.g pathogenic invasion)
Local inflammatory response
Is important to clear an infection
Widespread systemic response
Can cause septic shock and death (especially in bacterial infections)
What are the 7 basic stages of inflammation?
1) Tissue is damaged and released inflammatory mediators (aka: cell-signalling molecules).
2) Inflammation occurs
3) The permability of the endothelium increases.
4) Blood accumulation
5) Clotting factors (plasma proteins) leak out of the endothelium
6) Blood clot forms
7) CHEMOTAXIS of white blood cells (neutrophils & macrophages)
8) Initiation of tissue repair.
What is pus filled with?
What causes fever and what are the 2 benefits of it?
The hypothalamus stimulates an increase in body temperature.
1) Inhibits bacterial growth
2) Speeds up enzyme activity which aids tissue repair.
What is the adaptive immune system?
A system of tissues, cells and molecules that carry out specific defence mechanisms
What are the 3 characteristics of the adaptive immune system?
3) Can discriminate between 'SELF' & 'NON-SELF' cells
What types of cells are involved in adaptive immune response (and 2 subtypes)?
Lymphocytes - B lymphocytes (B-cells) & T lymphocytes (T-cells)
What are the basics behind how adaptive immune responses occur?
1) The lymphocytes are able to recognise the non-self cells (pathogens) due to the EPITOPE (part of the antigens - on their cell surface membranes)
2) The epitopes will have a specific-binding site (due to gene arrangement)
3) Only the lymphocytes that complement this specific-binding site are used in the adaptive immune response
4) Specific interaction of these lymphocytes with the antigen on the surface membrane of the pathogen.
5) Activates the lymphocyte
6) Some of these specific lymphocytes will divide, proliferate and DIFFERENTIATE into EFFECTOR CELLS.
7) Some of these specific lymphocytes will proliferate into MEMORY CELLS.
What do the specific lymphocytes differentiated into the effector cells do?
Eliminate the 'non-self' (pathogen)
Describe the derivation and differentiation of T cells and B cells?
1) The bone marrow stores pre - T cells and pre B - cells (virgin antigen-sensitive lymphocytes)
2) In the thymus, the pre - T cells will develop into T - cells (mature antigen-sensitive lymphocytes)
3) In the bone marrow, the pre - B cells will develop into B cells (mature antigen-sensitive lymphocytes)
What is the name of the 2 types of immunity carried out by each of the lymphocytes (involved in adaptive immune response)?
T - cells (cell-mediated immunity)
B - cells (antibody-mediated immunity)
5 functions of the T-lymphocytes:
1) (Cytotoxic T-cells) Kills virus-infected cells
2) (T-helper cells) Help in antibody-mediated immune response
3) Activates macrophages
4) Resistance of intracellular pathogens
5) Immunoregulation function
What are the 2 types of T- cells?
CD4 and CD8
What do the 2 types of T-cells have in common?
They are both glycoprotein markers. They both have a specific T-cell receptor on their surface membrane. This T-cell is able to detect antigens from the pathogens - that are PRESENTED on the surface of the innate immune system cells.
How are the antigens from the pathogens PRESENTED on the surface of the innate immune system cells?
The antigens will need to be bound to an MHC molecule in order to be presented on the surface of innate immune system cells.
So that, the T-cell receptors on the surface of CD8 and CD4 are able to recognise the antigens.
What are the 2 classes of MHC molecules and where are they found?
MHC Class 1 (found on cells with a nucleus)
MHC Class 2 cells (found on professional antigen-presenting cells)
What antigens are presented by the MHC Class 1 molecules, which type of T cell do they present it to and what do they cause this type of T cell to do?
1) MHC Class 1 molecules present the antigens that have a intracellular origin (e.g. viruses)...
2)...to the CD8 T-cells.
3) This causes the CD8 T-cells to become cytotoxic T-cells (that kill virus-infected cells)
What antigens are presented by the MHC Class 2 molecules, which type of T cell do they present it to and what do they cause this type of T cell to do?
1) MHC Class 2 molecules present the antigens that have an extracellular origin (e.g bacterias)...
2) ... to CD4 T-cells
3) This causes the CD4 T-cells to become T-helper cells.
What are the 3 functions of the T-helper cells?
1) Help in antibody-mediated immunity.
2) Activate macrophages
3) Help the CD8 T-cells to become cytotoxic T-cells
When the specific B-lymphocyte comes in contain with its complementary antigen (on the surface of a pathogen) what 2 things occur?
2) Some will divide, proliferate and differentiate plasma cells
3) Some will proliferate into memory cells
What do B-lymphocytes that differentiate into plasma cells do?
They manufacture and export SPECIFIC antibodies (that will recognise specific antigens on the surface of pathogens).
What are antigens?
A large molecule. It is either made up of:
1) Proteins (most common)
What are antibodies also referred to as?
Can antibodies, that are produced by the same B-lymphocyte plasma cell, detect different antigens?
No. All of the antibodies produced by a single plasma cell are identical to eachother and so are only able to detect the same specific antigens.
Describe the structure of an antibody:
1) Two chains (heavy chain - longer and lighter chain - shorter)
2) Each chain is made up of different regions; constant, variable and hyper-variable regions
3) The variable and hyper-variable regions make up the antigen bindings sites (they will have a specific shape that will only complement a specific antigen).
4) One antibody has 2 antigen-binding sites
5) The 2 chains are held together by a DISULPHIDE BOND.
6) The disulphide bond creates a flexible hinge that allows the 2 antigen-binding sites to be of a variable distance away from eachother.
What chain is responsible for the antibody to have a different function?
What are the main classes of antibody?
Blood and tissue antibody. Binds to phagocytes and neutralises toxins. Fixes complements
1st antibody to be produced at the site of infection
Acts a receptor on the surface of B-lymphocytes. Fixes complements
Binds to basophils and mast cells. Important in multicellular parasite infection response
What are the 3 ways in which antibodies fight against infection?
1) Block pathogens and toxins binding to cells
2) Facilitate phagocytosis (carried out by innate immune system cells)
3) Kill bacteria by activating its complement
Which class of antibody will be the main one involved in blocking pathogens and toxins from binding to cells?
How does the antibody (IgG) block the binding of a pathogen or toxin to a cell?
1) The specific antibody that's binding site is specific to the toxin/pathogen antigen will make a complex.
2) This prevents the toxin/antigen from making a complex with the cell's receptor.
3) The antibody will then bind to a phagocyte (innate immune cell) and phagocytosis will occur.
4) The antibody will neutralise the toxins.
5) As the cell's receptor has not made a complex with the pathogen/toxin - it will survive.
For which particular pathogen, is the antibodies role of facilitating phagocytosis by innate immune system cells, important for?
Immune system defence against ENCAPSULATED BACTIERIA.
How does the antibody kill the bacteria through activating its complement?
1) Antibody binds to the bacteria and activates its complement.
2) The complement will then bind to the bacteria.
3) This causes a release of CYTOKINES (inflammatory mediators) - increases permeability of the blood endothelium and cytotaxis of the innate immune system cells that carry out phagcytosis
4) The complement will facilitate phagocytosis by:
- Coating the bacteria
- Punching holes in the bacteria - leads to extracellular lysis of the bacteria