Immunology Flashcards
What is the immunological role of mucus membranes?
Prevents attachment of pathogens
Continuously shedded to remove any pathogens which do attach
Describe the innate immune system?
Non specific- Will produce the same response time and again to invading pathogens
Describe the adaptive immune system?
Highly specific; Exhibits immunological memory; Involves antibody production
Describe the process of phagocytosis.
Phagocyte surrounds and engulfs pathogen
Encloses pathogen in phagosome
Phagosome fuses with lysosome
Lysosome releases cocktail of hydrolytic enzymes onto pathogen
Pathogen is digested
Remains often ‘burped’ out and acts as signal to other immune cells.
What leukocytes are phagocytic?
Macrophages (and so monocytes), Granulocytes (neutrophils, basophils and eosinophils).
What causes redness upon injury?
Macrophages release chemical signals to other cells when they encounter a pathogen. (This signal alerts cells of the invasion) These chemicals often restrict blood flow away from the site of injury, causing redness.
What are the 3 active complement pathways called?
Classical, Alternative and Lectin
Why can the complement system be considered innate?
It does not change over time
What is the argument for the complement system possibly not being part of the innate immune system.
It can be brought into action by the adaptive immune system
What shared outcome do all three complement pathways have?
Lysis of the target cell and/ or making pathogens more susceptible to phagocytosis.
Brief overview of complement process..?
About 20 individual proteins working together in an enzyme cascade to form a membrane attack complex which basically punches a hole in the pathogen, preventing it maintaining homeostasis- It dies
What is the most common complement protein?
C3
Which complement pathway(s) is/are effector mechanisms of the innate immune system?
Alternative and Lectin
Which complement pathway(s) is/are effector mechanisms of the adaptive immune system
Classical
What is MAC?
Complement legions in the membrane of erythrocytes, formed by poly C9
How do Natural Killer cells destroy cells?
- Secrete perforin onto a cell to bore holes in it, creating a MAC. Enzymes then secreted which enter cell via hole, causing cell to commit suicide.
- Use of FasL protein to connect with Fas protein on target cell, giving target cell the signal to commit suicide.
What are cytokines?
Chemicals used by cells to communicate with other cells.
What are the functions of complement? (4)
- Lysis of Pathogens
- Stimulates phagocytosis of microbes
- Stimulates inflammation by activating mast cells and neutrophils
- Stimulates activation of B cells and antibody production
Describe autocrine action of cytokines?
Cell using cytokines for self stimulation
Describe paracrine action of cytokines?
Cell using cytokines to stimulate another (local) cell.
Describe endocrine action of cytokines?
Cell releasing cytokines into the circulatory system to stimulate another (distant) cell
What are the functions of the lymphatic system?
- Drainage of tissue
- Absorption/ transport of fats/ fatty acids to circulatory system
- Immunity
How is lymph formed?
ISF entering channels of lymphatic system
How is lymph moved around the system?
Contractions of the skeletal muscles
Name the sight of blood production
Bone marrow
Examples of secondary lymphoid organs
Lymph nodes; Spleen; Mucosal associated lymphoid tissue
What is the role of secondary lymphoid organs in immunity?
These are the sites of lymphocyte activation by antigens
Examples of primary lymphoid organs
Bone marrow and Thymus
What is the role of primary lymphoid organs in immunity?
Where B and T lymphocytes are produced and receive their early training.
What is one secondary lymphoid organ d=feature which the spleen lacks?
High Endothelial Venules
What are High Endothelial Venules?
Doorway to which B and T cells enter secondary lymphoid organ from the blood.
How do antigens gain access to Peyer’s Patch (MALT)?
Presence of M cells
These M cells use endosomes to transport antigens from the intestinal lumen into the Peyer’s Patch.
What is the role of T cells?
Cell mediated immunity
Assisting B cells
What is the role of CD4+ T cells?
Assisting B cells
What is the role of CD8+ T cells?
To destroy invading cells- They are cytotoxic to cells
What is the role of MHC Class I?
Presents ‘virtually induced’ peptides to CD8+ T cells to produce cytotoxic response.
How do Cytotoxic T cells work?
Release perforin to form pores in target cell
Secretes Granzyme B onto pores on target cell which enter and induce cell apoptosis.
How do memory B cells work?
Once sensitised to particular antigen, if presented with same antigen again, will release antibodies that bind to it with greater affinity.
How do memory T cells work?
Once sensitised to particular antigen, if presented with same antigen again, will react much more quickly.
In terms of lymphocytes, what does the term naïve mean?
The lymphocytes have not yet been in contact with a particular antigen and are, therefore, immunologically inexperienced.
What is natural active immunity?
Infection occurs and lymphocytes are activated by antigens on the surface of pathogens. Own antibodies produced.
What is natural passive immunity?
Mother passes antibodies to child via placenta or colostrum
What is artificial passive immunity?
Antibodies injected from another source, no memory cells produced. This is used as an emergency response to a fatal disease- E.g. a tetanus shot
What is artificial active immunity?
Injection or swallowing of modified antigens to stimulate lymphocyte cells without the risk of infection. Own antibodies and memory cells produced. This is the idea of a vaccination.
What is the difference between B cells and plasma cells?
B cells mature into plasma cells which are then responsible for antibody production.
Define antigen
Any substance capable of provoking an immune response
Describe the structure of an antibody
Light chain (either lambda or kappa) and longer heavy chain
Antigen binding site and FC site
Contains disulphide bond
What are the 5 classes of antibody?
IgG; IgA; IgM; IgE; IgD
What is the role of IgG?
Makes cells more susceptible to phagocytosis (opsonizer)
What is the role of IgA?
Protects mucosal surfaces, resistant to stomach acid
What is the role of IgM?
Promotes compliment and phagocytosis
What is the role of IgE?
Defends against parasites, causes allergies and anaphylactic shock
