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Flashcards in Foundations in Immunology Deck (34):

List the major cell types involved with the innate immune response



List the major cell types involved in the adaptive immune response

Lymphocytes (T and B cells)


Describe the main role of the innate immune system

The innate immune system acts as the body’s first line of defence. It involves the use of:
o Physical Barriers
• Tight junctions between epithelia
• Mucous membranes
o Phagocytic cells
• Macrophages
• Neutrophils
o Soluble factors


Describe the function of natural killer cells

Kills tumour and virally infected cells, through two different methods:
• Degranulation - bore holes in target cells by secreting perforin onto them and forming a MAC
• FasL-dependent cell suicide dependent on the expression of both inhibitory and activating receptors. Inhibitory receptors on the NK cells recognise and bind to MHC1


Describe the process of phagocytosis and intracellular killing

Phagocytosis is triggered when the phagocyte recognises a foreign cell. It is the internalization of foreign matter by cells into cytoplasmic vesicles. Once inside, the matter is digested following the fusion of the phagosomes to the lysosomes , which contain degradative enzymes.


Define the primary lymphoid organs and their function

These organs are where lymphocytes are generated.
• Thymus
• Bone marrow
• Foetal liver


Define the secondary lymphoid organs and their function

Where immune responses are initiated and lymphocytes maintained.
• Lymph Nodes
• Spleen


Describe the fundamental properties of the adaptive immune response

o Specificity
o Diversity
o Memory
o Recruitment of other defence mechanisms


Describe the role of B lymphocytes in immunity

B cells differentiate further to form plasma cells. These cells synthesise antibodies specifically designed for use against the detected pathogen. The pathogen is recognised first by membrane bound antibody. The antibodies produced by plasma cells are soluble in plasma, and upon recognition of the particular antigen they are against, produce a must faster immune response that upon first encounter.


Illustrate the structure and function of an antibody

The section which binds to the antigen is known as the paratope, and it binds to the antigen epitope.

Antibodies are made up by two heavy chains and two light chains, making up constant regions (mediate effector reactions) and variable regions (recognise specific Ags, what gives Ab its specificity). The chains are held together by disulphide bonds.


What is an antigen?

Antigens are proteins able to evoke an immune response and react with immune products.


Briefly describe the complement system and its function

The complement system is made up of 25 serum proteins whose sequential activation and assembly into functional units can bring about three events.
o Recruitment of inflammatory cells
o Coating/Opsonisation of Bacteria
o Lysis of bacteria


Describe how antigen presenting cells and T lymphocytes interact

MHC class II is found only on ‘Professional Antigen Presenting Cells’ (APCs) and it prresents exogenously produced Ag to CD4+ T cells to activate macrophages and B cells and produce a innate immune response to clear any infections.

All cells possess MHC class I, which presents internal antigens or viral peptides to CD8+ Tc cells to initiate cell death of the infected cell.


Describe the role of Th1 and Th2 cells in the immune response

Proliferating helper T cells that develop into effector T cells differentiate into two major subtypes of cells known as Th1 and Th2 cells.
o Th1 helper cells are the host immunity effectors against intracellular bacteria and protozoa.
o Th2 helper cells are the host immunity effectors against extracellular parasites including helminths.


Describe the role of cytokines

Cytokines are small chemical messengers used by cells to communicate with other cells to coordinate immune reactions. They can act in an autocrine, paracrine and endocrine fashion.


Give 5 examples of pathogens

• Virus
• Protozoa
• Bacteria
• Fungi
• Parasite


What is tolerance?

One of the most remarkable properties of the immune system is its ability to react to foreign antigen and yet not to react to self antigen. This is vitally important for the health of the host. Immunological unresponsiveness to an antigen is called tolerance. Self-tolerance is maintained by a number of mechanisms including the elimination of lymphocytes which react to self antigens or self markers in their early stages of development and allowing lymphocytes to encounter self antigens in a setting which leads to their destruction if they react to these self antigens


Describe the fundamental properties of the innate immune response

First line of defence
No memory


Name two professional phagocytes



Describe the functions of eosinophils

Release granules to combat large extracellular pathogens, though alongside mast cells can play a role in allergy and asthma.


What causes anaphylactic shock?

• Anaphylactic shock caused by mast cell degranulation
• Mast cells protect against parasites and contain many granules containing pharmacologically active chemicals, including histamine.
• On first exposure to an allergen (e.g. some people make lots of IgE antibodies against the allergen. Mast cells have receptors on their surfaces which can bind to the Fc region (the constant end) of the IgE antibodies.
• On second exposure to the allergen the IgE antibodies which are bound to the mast cell can now also bind the allergen. This drags the mast cell receptors together and results in a signal being sent to release the chemicals inside the cell into the tissues. This increases capillary permeability allowing fluid to escape from the blood vessels – runny nose and watery eyes. This is usually a local effect but if the toxin spreads throughout your body and triggers massive mast cell degranulation the effects can be serious – blood volume can reduce so much that blood pressure drops massively and the heart can no longer pump efficiently resulting in heart attack. Also, histamine can cause your airway to constrict making it difficult to breathe and can cause suffocation.


What make up non-specific humeral factors?

Within body fluids (and mucus) is a variety of soluble substances with protective functions:
o Growth Inhibitors
o Enzyme Inhibitors
o Lysins
o Complement Proteins


Describe acute and chronic inflammation

• Acute inflammation is initial response of the body to harmful stimuli
• Chronic inflammation leads to a progressive shift in the type of cells which are present at the site of inflammation and is characterised by simultaneous destruction and healing of the tissue from the inflammatory process.


Describe the lymphatic system and its function

The lymphatic system is a network of conduits that carry a clear fluid called lymph and includes the lymphoid tissue through which the lymph travels.
The functions of the lymphatic system include:
o Drainage of interstitial fluids from tissue
o Absorption and transport of fatty acids as chyle to the circulatory system
o Immunity


Describe the structure of lymphatic vessels

Only carry fluid from tissues in one direction.
Smallest are the lymphatic capillaries (blind-ended sacs, highly permeable).
Walls are composed of endothelium in which simple squamous cells overlap to form one-way valves.


What occurs in positive selection?

Positive selection "selects for" T cells with TCRs capable of interacting with MHC with weak affinity . Positive selection involves the production of a signal by double-positive precursors that express either MHC Class I or II restricted receptors


What occurs in negative selection?

Negative selection removes thymocytes that are capable of strongly binding with "self" MHC peptides.


Define active immunity

Active immunity is conferred by a host response to a microbe or microbial antigen. Can have immunological memory


Define passive immunity

Passive immunity is conferred by adoptive transfer of antibodies or T lymphocytes specific for the microbe e.g. transfer of maternal Abs. No memory.


Describe the development of B cell tolerance

• Central tolerance development in B cells - Immature B cells that recognize self antigens in the bone marrow with high avidity (e.g., multivalent arrays of antigens on cells) die by apoptosis or change the specificity of their antigen receptors (receptor editing). Weak recognition of self antigens in the bone marrow may lead to anergy (functional inactivation) of the B cells.
• Peripheral T cell tolerance in B cells - B cells that encounter self antigens in peripheral tissues become anergic or die by apoptosis. In some situations, recognition of self antigens may trigger inhibitory receptors that prevent B cell activation.


Define a pathogen

A pathogen is any microorganism that causes disease – bacteria, virus, parasite.


Define a antigen

Any substance capable of triggering an immune response is called an antigen. An antigen can be a virus, a bacterium, a fungus, or a parasite, or even a portion or product of one of these organisms


Define an epitope

An antigen announces its foreignness by means of intricate and characteristic shapes called epitopes, which protrude from its surface. Most antigens, even the simplest microbes, carry several different kinds of epitopes on their surface; some may carry several hundred. However, some epitopes will be more effective than others at stimulating an immune response.


Describe the two types of B cell activation

• T cell dependent activation requires a signal from the clustered BCR along with a signal form a T cell in which a protein on the surface of a T cell which recognises the same antigen as the B cell binds to a receptor on the B cell.
• T cell independent activation can happen when huge numbers of BCR are clustered together by an antigen with a very large number of repeated epitopes – a mitogen.