Week 2 - General pathological mechanisms Flashcards
What site are antibacterial factors commonly found at?
Mucosal surfaces i.e. nose, back of throat
Lysozyme is an antibacterial factor. How does it fight infection?
Breaks down the gram positive cell wall of bacterial cells.
Lactoferrin is an antibacterial factor. How does it fight infection?
Inhibits bacterial growth through iron chelation.
What are the three potential outcomes of the complement pathway?
Recruitment of inflammatory cells, opsonization of pathogens, killing of pathogens.
List 3 functions of macrophages.
Phagocytosis
Cytokine production
Antigen presentation
List 3 function of neutrophils.
Phagocytosis
Chemotaxis
Degranulation (release factors which kill microbes.)
Which WBC characteristically produces pus?
Neutrophils
Which WBC targets parasites and has a role in allergy?
Eosinophils
The degranulation of which WBC causes the histamine mediated weal and flare reaction?
Basophils
Which immune cell can initiate an an adaptive immune response by presenting antigens to CD4 T cells in the lymph node?
Dendritic cells
Which type of adaptive immune cells predominantly targets extracellular pathogens such as bacteria?
B cells
Which type of adaptive immune cells predominantly targets intracellular pathogens i.e. viruses?
Cytotoxic T cells
What is the role of CD4 helper T cells?
Activates B cells and Killer T cells in response to antigen presentation.
What are the three roles of antibodies?
Opsonize pathogens for phagocytosis, activate complement for lysis and neutralise toxins and pathogen binding sites
Which antibody looks like a star, is present in the primary immune response and has a low affinity?
IgM
Which antibody is the main antibody of the secondary immune response and has a high affinity?
IgG
Which antibody is present in secretions and lines epithelial surface and looks like two antibodies standing end to end?
IgA
Which antibody has a high affinity and binds to mast cells, having a role in allergy?
IgE
Describe the process by which autoimmunity is prevented as B cells and T cells are produced.
B cells undergo screening in the bone marrow and T cells in the thymus. If they strongly bind to self antigens they are destroyed by apoptosis.
What cells are MHC class 1 found on? To what cells do they present antigens to?
All nucleated cells
CD8 killer T cells
What cells are MHC class 2 found on? To what cells do they present antigens to?
Antigen presenting cells
CD4 helper T cells
Type I (allergic/atopic) hypersensitivity is mediated by…
IgE bound to mast cells
Type II hypersensitivity is mediated by…
IgM or IgG bound to cell/matrix antigen
Type III hypersensitivity is mediated by…
IgM or IgG bound to soluble antigen
Type IV hypersensitivity is mediated by…
CD4 or CD8 T cells
Type V (which is sometimes considered a subgroup of Type II) is mediated by…
IgM or IgG bound to receptors
What are the six stages of allergic response?
- Sensitisation
- Mast cells primed with IgE
- Re-exposure to antigens
- IgE binds to antigens
- Mast cells degranulate
- Pro-inflammatory response stimulates and amplifies future responses
Name 3 things that are released when mast cells degranulate as part of the allergy process.
Histamine pro-inflammatory cytokines chemokines prostaglandins leukotrienes
The early phase response in type I hypersensitivity occurs minutes after exposure to allergen. What changes occur in body tissues this phase? What mediates this phase?
Increased vascular permeability and smooth muscle contraction. Prostaglandins and histamine.
The late phase response in type I hypersensitivity occurs over hours/days after exposure to allergen. What changes occur in body tissues this phase? What mediates this phase?
Sustained smooth muscle contraction and tissue remodelling. Mediated through recruitment of T cells and other immune cells to site.
Why is anaphylaxis an immediate danger to life?
Increased vascular permeability causes:
Soft tissue swelling, threatening the airway
Loss of circulatory volume, causing shock
What are the three stages of type II hypersensitivity?
- Sensitisation
- Opsonisation of cells
- Cytotoxicity (through complement activation)
Type III hypersensitivity is mediated by immune complexes bound to soluble antigens. Where do these immune complexes accumulate? What is the effect of this?
They accumulate in small blood vessels.
Occlusion of blood vessels, complement activation and perivascular inflammation.
In type 4 hypersensitivity, how long does it take for the reaction to occur?
Several days after exposure to the antigen.
Type 1 diabetes is an autoimmune disease. What types of hypersensitivity is it caused by?
Type II and type IV
In myasthenia gravis, what causes the fatigueable muscle weakness? What type of hypersensitivity is this?
IgG binds to ACh receptor, preventing signal transduction required for muscle contraction. Type 5.
Name two systemic autoimmune diseases.
Rheumatoid arthritis and inflammatory bowel disease.
What protein is a good indicator for rheumatoid arthritis?
Anti-citrullinated protein
Inflammation is the universal response to tissue damage. 1. Name three causes of tissue damage that result in inflammation.
2. What is the purpose of inflammation?
- Infection, trauma, necrosis
2. Destroy or control the harmful stimulus, initiate repair and restore function.
What are the 5 clinical signs of inflammation and what causes them?
Redness - caused by hyperaemia (increased blood flow)
Swelling - fluid exudate and hyperaemia
Heat - hyperaemia
Pain - release of bradykinin and PGE2 (prostaglandin E2)
Loss of function - all of the above
Vascular dilatation occurs during inflammation. What 3 factors cause blood vessels to dilate? How does vascular dilatation cause swelling?
Histamine (from mast cells), prostaglandins, NO.
As the blood flow is increased, you get more fluid passing into tissues causing swelling.
During inflammation neutrophils are activated. What three factors cause neutrophils to be actiavted?
C5a, bacterial products, leukotriene B4
Vascular endothelial activation occurs during inflammation. Name 3 factors that causes this.
5HT, Histamine, C5a
Endothelial activation allows plasma proteins to leak out into the endothelium. Name three of these proteins.
Complement, immunoglobulin, fibrinogen.
An exudate is a fluid that has leaked out of a blood vessel into the extracellular space. Name 3 exudates.
Neutrophilic (purulent)
Fibrinous
Serous
What are some of the main ways that infection can spread?
Through natural barriers, in the air, in the blood, through weakened immune system (i.e. HIV, steroid use)