Immunology Flashcards
What is meant by tolerance?
Immunological unresponsiveness to an antigen.
What are the main physical barriers to infection?
Reproductive, respiratory and digestive tract and the skin.
What cells produce mucus?
Goblet cells
Into what two sections is the immune system divided?
Innate and adaptive.
Which cells are phagocytic?
Monocytes, dendritic cells and macrophages
All granulocytes
Describe the process of phagocytosis.
Phagocyte surrounds and engulfs bacterium, encasing it in intracellular phagosome.
Lysosome containing cocktail of powerful hydrolytic enzymes fuses with phagosome.
Enzymes digest bacterium, destroying it.
Debris is released into extracellular space by exocytosis and acts as a signal to other immune cells.
Into what two cell types can a monocyte mature?
Dendritic cells
Macrophages
What is the most abundant WBC?
Neutrophil
For how long do neutrophils generally circulate in the blood before undergoing apoptosis?
6 Hours
Where are all blood cells produced?
Bone marrow
In what type of infection are eosinophils mainly involved?
Parasitic
What type of WBC is a mast cell?
Granulocyte
What type of hypersensitivity are mast cells involved with?
Type 1- Allergy
What is the least common granulocyte cell?
Basophil
Name 4 non-specific humoral molecules which protect against infection.
- Lysins
- Growth inhibitors
- Enzyme inhibitors
- Complement proteins
What causes redness upon injury?
When macrophages encounter a pathogen, they release chemicals to alert other cells to invasion. These chemicals often restrict blood flow away from the site of invasion. This causes redness
Describe the adaptive immune system.
Specific- Exhibits immunological memory and antibody production
Describe the innate immune system.
Non-specific- Produces the same response for every infection.
What are the three compliment pathways.
Classical
Alternative
Lectin
Give a brief overview of the complement pathway.
Over 20 individual proteins, working together in an enzyme cascade to form a membrane attack system. This basically works by punching a hole in the pathogen, preventing it from maintaining homeostasis and killing it.
What is the argument for the complement system being part of the innate immune system?
It does not change its mechanism at all over time, with subsequent infections.
What is the argument for the complement system being part of the adaptive immune system?
The adaptive immune system activates these pathways
Which complement pathway is an effector mechanism of the adaptive immune system?
Classical
Which complement pathways are effector mechanisms of the innate immune system?
Alternative and Lectin
What is the central event in activation of the complement system?
Proteolysis (breakdown into smaller peptides) of complement protein C3
What is meant by MAC?
Membrane attack complex
By what two mechanisms of action can a natural killer cell destroy a target cell?
- Secretion of perforin onto target cell, creating a MAC which bore hole into the cell. Secretion of enzymes into this hole will digest the target cell.
- Protein FasL on NK cell binds to protein Fas on target cell. This binding sends a signal to target cell to commit suicide.
What are cytokines?
Chemicals used in cell-to-cell communication, specifically in communicating presence of invading microorganism.
What are the three mechanisms of action of cytokines?
- Autocrine- self activation
- Paracrine- Activation of local cell
- Endocrine- Spread via circulation and activation of far away cell.
What are the functions of the lymphatic system?
- Drainage
- Absorption and transport of fats and fatty acids.
- Immunity
What are the primary lymphoid organs?
Bone marrow and Thymus
What are the immunological functions of the bone marrow?
Production of Lymphocytes and storage of B lymphocytes.
What is the immunological function of the thymus?
Site of maturation of T Lymphocytes.
What are the secondary lymphoid organs?
Spleen, Tonsils. Lymph Nodes, Peyer’s patch.
What is the main immunological function of the spleen?
Filter the blood of antigens, defective microorganisms and worn out RBCs
What is one secondary lymphoid organ feature which the spleen lacks?
High Endothelial Venules
What are High Endothelial Venules?
Doorway to which B and T cells enter secondary lymphoid organs from the blood.
What is the role of CD4+ T cells?
To assist B cells
What is the role of CD8+ T cells?
Cytotoxic cells which destroy invading cells
How do memory B cells work?
Once sensitised to a particular antigen, if presented with that antigen again, will produce antibodies that bind to it with greater affinity.
How do memory T cells work?
Once sensitised to a particular antigen, if presented with that antigen again, will produce a quicker response.
In terms of lymphocytes, what does the term naïve mean?
The lymphocytes have not yet been in contact with a particular antigen and so are immunologically inexperienced.
What is the difference between active and passive immunity?
Active immunity involves the host producing its own antibodies and T lymphocytes to combat infection.
Passive immunity involves adoptive transfer of antibodies and T lymphocytes from an outside source, to combat infection.
What is meant by opsonisation?
Making a foreign cell more susceptible to phagocytosis
What are the five classes of antibody?
IgG, IgM, IgE, IgA, IgD
What is the function of IgG?
Opsonisation
What is the function of IgM?
Opsonisation and fixing of complement cascade
What is the function of IgE?
Protection from parasites, involved in allergy and anaphylaxis.
What is the function of IgA?
Protection of mucosal surfaces
Describe the structure of an antibody?
Light Chain, either lambda or kappa.
Longer Heavy chain (5 types)- Decides which class of antibody it is.
Antigen binding site and Fc binding site
Disulphide bonds
What is the difference between B cells and plasma cells?
B cells mature into plasma cells which are then responsible for antibody production
What is an antigen?
Any substance capable of provoking an immune response.
Why is tolerance of T cells more important than tolerance of B cells?
Generally, antibody production by plasma cells (differentiated B cells) is stimulated by a form of T cell (T helper cell)
